r.  O’CONOR  SLOAN  E,  A.  M.,  E.  M„  Ph.  D. 


Franklin  Institute  Librart 

FHILdDELFHI4 


Class-.^-7-  S Book.S.i...>5r....  Accession. ..8..G.X-2... 


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Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/rubberhandstamps00sloa_0 


BY  THE  SAME  AUTHOR. 


aritbmetic  of  lElectridt?. 

A Complete  and  Indispensable  vade  mecum 
for  amateur,  student,  and  electrical 
engineer. 

Fully  Illustrated.  Price,  $1.00. 


Home  Experiments  in  Science. 

252  Pages.  96  Illustrations.  Price,  $1.50. 


Rubber  hand  stamps 

* * * * 4:. 


AND  THE 


^i^^5r;^pulation  of  *J!?ubber 


A PRACTICAL  '■'REATISR  ON  TRE  MANUPACTUE3  03"  IITDIA  RUBBER  HAND 
STAMPS,  SMALL  ARTICLES  OP  INDIA  RUBBER,  THE  HEKTOGRAPH, 
SPECIAL  INKS,  CEMENTS,  AND  ALLIED  SUBJECTS 


BY 

T.  O’CONOR  SLOANE,  A.M.,  E.M.,  Ph.D. 

Author  of 

“Home  Experiments  in  Science,”  “Arithmetic  of  Electricity,”  etc. 


KULLY  ILLUSTJRATED 


NEW  YORK 

NORMAN  W.  HENLEY  & CO. 

150  NASSAU  STREET 
1891 


PREFACE. 


The  present  work  hardly  needs  a preface.  The 
object  is  to  present  in  the  simplest  form  the  subject 
of  the  manipulation  of  india  rubber.  To  mould 
and  cure  the  mixed  gum  but  few  appliances  are 
needed,  and  these  can  be  made  at  home.  The  arti- 
cles produced  are  of  more  than  ordinary  utility. 
These  two  facts  give  value  to  the  art  and  furnish  a 
raison  (VHre  for  tliis  book.  If  its  instructions  do 
not  prove  practical  it  will  have  missed  its  object. 

For  some  reason  the  methods  of  moulding  the 
material  are  not  generally  known.  Experiment  has 
taught  many  the  futility  of  attempting  to  melt  and 
cast  it.  While  thus  intractable  by  the  usual  meth- 
ods, it  is  the  most  plastic  of  materials  when  prop- 
erly treated.  Its  power  of  reproducing  the  finest 
details  of  a mould,  of  entering  all  the  intricacies 
and  undercuttings  of  a design,  cause  one  to  feel  a 
peculiar  pleasure  in  working  with  so  responsive  a 
material.  It  is  not  saying  too  much  to  affirm  that 
to  some  readers  this  book  Avill  disclose  a long  hidden 
secret.  To  make  it  more  generally  useful  it  is  writ- 


IV 


PREFACK 


ten  for  such  readers,  to  meet  the  want  of  those 
knowing  of  the  subject.  It  was  felt  that  in  follow- 
ing this  course,  and  in  treating  the  subject  from  its 
first  steps,  including  the  simplest  as  well  as  most 
advanced  methods,  the  book  would  appeal  to  a 
larger  body  of  readers. 

The  allied  subjects  to  which  some  chapters  are 
devoted  will  be  acceptable  to  many  readers.  The 
hektograph  is  given  in  several  modifications.  A 
substitute  for  rubber  stamps  which  stands  the 
severe  usage  of  the  Post  Office  has  very  distinct 
merits,  and  the  manufacture  is  accordingly 
described  in  detail.  Cements  and  inks  embody 
many  special  formulae.  In  the  last  chapter  inter- 
esting and  practical  notes  will  be  found. 

For  the  use  of  certain  cuts  we  are  under  obliga- 
tions to  the  Buffalo  Dental  Manufacturing  Co., 
Messrs.  E.  & F.  N.  Spon  & Co.,  and  to  Mr.  L.  Spang- 
enberg. 


CONTENTS 


PAGE 

CHAPTER  I. 

THE  SOURCES  OF  INDIA  RUBBER  AND  ITS  HISTORY. 

The  Trees — The  Sap — Caoutchouc — Early  Uses  by 
the  Indians— First  knowledge  of  it  in  Europe — Good- 
year, Day,  and  Mackintosh 9 

CHAPTER  II. 

THE  NATURAL  HISTORY  AND  COLLECTION  OF  INDIA 
RUBBER. 

African,  East  Indian,  Central  and  South  American 
Gums — Differenc  Methods  of  Collection  and  Coagula- 
tion   15 

CHAPTER  III. 

PROPERTIES  OF  UNVULCANIZED  AND  VULCANIZED  IN- 
DIA RUBBER. 

Properties  of  Unvulcanized  Rubber;  its  Cohesion  and 
importance  of  this  property — Analysis  of  Sap  and 
Caoutchouc — Effects  of  Heat  and  Cold — Distillation 
Products — Vulcanized  Rubber,  and  its  Properties 24 

CHAPTER  IV. 

THE  MANUFACTURE  OF  MASTICATED,  MIXED  SHEET 
AND  VULCANIZED  INDIA  RUBBER. 

Treatment  by  the  Manufacturer — Washing  and  Sheet- 


vi 


CONTENTS. 


ing — Masticating — Making  Sheeting  and  Threads — Mix- 
ing— Curing — Coated  Tissues 35 

CHAPTER  V. 

INDIA  KUBBER  STAMP  MAKING. 

Mixed  Sheet— Outlines  of  Moulding — Home-Made  * 

Vulcanizing  Press — Further  Simplifications  of  Same — 
Securing  Accurate  Parallelism  of  Platen  and  Bed — Dis- 
tance Pieces — Wood  vs.  Iron  as  Material  for  Press — 

Use  of  Springs  on  the  Home-Made  Press — Metal  Flask 
Clamps — Large  Gas-Heated  Vulcanizing  Press — Prepar- 
ing Type  Model — The  Matrix — Plaster  of  Paris  and 
Dental  Plaster  as  Substances  for  Matrices — Dextrine 
and  Gum  Arabic  Solutions  for  Mixing  Matrix — How 
Matrix  is  made — Shellac  Solution  for  Matrix — Matrix 
Press  and  Spring-Chase — How  to  retard  the  Setting  of 
Plaster  of  Paris — Oxychloride  of  Zinc  Matrices — Talc 
Powder — Moulding  and  Curing  the  Stamp — Kerosene 
Heating  Stove — Manipulation  of  Press — Degree  of  Heat 
— Simple  Test  of  Curing — Time  Required — Combined 
Matrix  Making  and  Vulcanizing  Apparatus — Chamber 
Vulcanizers — Object  of  Steam  in  Vulcanizers — Temper- 
ature Corresponding  to  Different  Steam  Pressures — 
Jacketed  Vulcanizers — Gas  Regulator — Flower  Pot 
Vulcanizer — Fish  Kettle  Vulcanizer — Making  Stamps 
without  any  Apparatus  Whatever — Notes  on  Type, 
Quadrats  and  Spaces — Autograph  Stamps 47 

CHAPTER  VI. 

INDIA  RUBBER  TYPE  MAKING. 

Movable  Type  Making — Simple  Flask  and  Matrix — 
Precautions  as  to  Quantity  of  Rubber — Moulding — 
Curing — Cutting  Type  Apart — Special  Steel  Moulds — 
Wooden  Bodied  Type 73 


CONTENTS. 


Vll 


CHAPTER  yiL 

THE  MAKING  OF  STAMPS  AND  TYPE  FROM  VULCAN- 
IZED INDIA  RUBBER. 

Ready  Vulcanized  Gum  as  Material  for  Stamps — 
Simplicity  of  the  Process  of  Usin^  It — Advantages 
and  Disadvantages — Availability  for  Type. 77 

CHAPTER  VIII. 

VARIOUS  TYPE  MATRICES  FOR  RUBBER  STAMPS  AND 
TYPES. 

Electrotype  Matrices — Papier  Mache — Flong  Paste — 
Flong  Matrices — Beating  into  Model — Drying  and  Bak- 
ing— Struck-up  Matrices — Chalk  Plates 80 

CHAPTER  IX. 

THE  MAKING  OF  VARIOUS  SMALL  ARTICLES  OF  INDIA 
RUBBER. 

Suction  Discs — Pencil  Tips — Cane  and  Chair  Leg 
Tips— Corks — Mats — Cord  and  Tubes— Bulbs  and  Hol- 
low Toys 85 

CHAPTER  X. 

THE  MANIPULATION  OF  SHEET  RUBBER  GOODS. 

Sheet  Rubber  Articles — Toy  Balloons — Uses  of  Sheet 
Rubber  in  the  Laboratory 94 

CHAPTER  XL 

VARIOUS  VULCANIZING  AND  CURING  PROCESSES. 

Liquid  Curing  Baths— Sulphur  Bath— Haloids  and 
Xitric  Acid  as  Vulcanizers — Alkaline  Sulphides — Sul- 
phur Absorption  Process— Parke’s  Process 97 

CHAPTER  XII. 

THE  SOLUTION  OF  INDIA  RUBBER. 

Mastication  with  Solvent— Peculiarities  of  the  Pro- 


viii  CONTENTS. 

cess — Different  Solvents  and  their  Properties — Paraffin 
— Vulcanized  Kubber  Solution — Aqueous  Solution 108 

CHAPTER  XIII. 

EBONITE,  VULCANITE  AND  GUTTA-PERCHA. 

Ebonite  and  Vulcanite — Manufacture — Manipulation 
— Gutta-Percha  and  its  Manipulation  108 

CHAPTER  XIV. 

GLUE  OR  COMPOSITION  STAMPS. 

Substitute  for  Rubber  Stamps — The  United  States 
Government  Formula — Models  and  Moulds — Dating — 
Handles 118 

CHAPTER  XV. 

THE  HEKTOGRAPH. 

How  Made — The  French  Government  Formula — Hek- 
tograph  Sheets 121 

CHAPTER  XVI. 

CEMENTS. 

Marine  Glue,  and  other  special  Cements 125 

CHAPTER  XVII. 

INKS. 

Hektograph,  Stencil  and  Marking  Inks — White  and 
Metallic  Inks 129 

CHAPTER  XVIII. 

MISCELLANEOUS. 

Preservation  and  Renovation  of  India  Rubber — 
Burned  Rubber  for  Artists — India  Rubber  Substitutes 
— General  Notes  of  Interest 134 


RUBBER  HAND  STAMP  MAKING 
AND  THE  MANIPULATION 
OF  RUBBER. 


CHAPTER  1. 

THE  SOUKCES  OF  RUBBEE  AND  ITS  HISTORY. 

India  rubber  or  caoutchouc  is  a very  peculiar 
product,  which  is  found  in  and  extracted  from  the 
juice  of  certain  trees  and  shrubs.  These  are  quite 
numerous  and  are  referred  for  the  most  part  to  the 
following  families:  Euphorbiaceaed,  Urticaceaed,  Ar- 
tocarpeaed,  Asclepiadaceaed,  and  Cinchonaceasd.  It 
is  evident  that  a considerable  number  of  trees  are 
utilized  in  commerce  for  its  production,  and  it  is 
certain  that  it  exists,  quite  widely  distributed,  in 
many  cases  as  a constituent  of  the  juice  of  plants 
not  recognized  as  containing  it. 

When  an  india  rubber  tree  is  tapped,  which  is 
effected  by  making  incisions  in  the  bark,  the  sap  of 
the  tree  exudes.  It  is  a milky  substance  and  is 
collected  in  various  ways;  it  may  be  in  vessels  of 


10 


BUBBEE  HAND  STAMP  MAKING 


clay,  in  shells,  or  in  other  receptacles  by  the  India 
rubber  hunters.  If  this  substance  is  examined  it  is 
found  to  be  of  very  remarkable  and  characteristic 
constitution,  resembling  in  its  physical  features 
ordinary  milk.  It  is  composed  of  from  fifty  to 
ninety  per  cent,  of  water,  in  which  is  suspended  in 
microscopic  globules,  like  the  cream  in  milk,  the 
desired  caoutchouc  or  India  rubber.  If  the  juice  is 
left  to  stand  in  vessels,  like  milk  in  a creamery,  the 
globules  rise  to  the  surface,  and  a cream  of  india 
rubber  can  be  skimmed  off  from  the  surface.  If 
the  juice  is  evaporated  over  a fire,  the  water  escapes 
and  the  india  rubber  remains.  By  dipping  an 
article  repeatedly  in  the  juice  and  drying  it,  a thick 
or  thin  coating  of  india  rubber  can  be  developed. 
Before  the  modern  methods  for  the  manipulation  of 
the  gum  had  been  developed,  and  before  the  inven- 
tion of  vulcanization,  this  method  Avas  adopted  for 
the  manufacture  of  shoes.  The  original  india 
rubbers  for  protection  of  the  feet  in  wet  weather 
were  made  in  this  manner.  A clay  last  was  used, 
upon  Avhich  the  india  rubber  Avas  deposited  as 
described.  The  clay  last  was  then  broken  out  and 
removed.  Great  quantities  of  overshoes  were  thus 
made  in  South  America,  and  many  were  exported  to 
Europe. 

When  caoutchouc  has  once  been  removed  from 
this  watery  emulsion,  which  for  all  practical  pur- 
poses is  a solution,  it  cannot  be  restored  to  the 
former  state  of  liquidity;  it  remains  solid.  It  Avill 


ANB  THE  MANIPULATION  OF  RUBBER.  11 


absorb  a considerable  quantity  of  water,  but  will 
not  enter  again  into  the  quasi  solution  or  combina- 
tion. This  property  of  permanent  coagulation, 
which  interferes  to  a degree  with  its  easy  manipula- 
tion, was  early  discovered.  In  the  last  century 
quantities  of  the  natural  milk  were  exported  to 
Europe  to  be  used  in  what  may  be  termed  the  nat- 
ural process  of  manufacture,  because  once  solidified 
it  could  not  be  redissolved,  and  because  the  manu- 
facturers of  those  days  had  not  the  present  methods 
of  dealing  with  the  apparently  intractable  gum. 

The  natives  of  South  America  before  the  advent 
of  Europeans,  were  familiar  with  the  treatment  of 
the  juice  by  evaporation  just  described  and  used  to 
make  bottles,  shoes  and  syringes  of  it  for  their  own 
use.  The  name  Siplionia  applied  to  several  species 
of  rubber  tree,  and  seringa  (caoutchouc)  and 
seringari  (caoutchouc  gatherer)  in  Spanish  recall 
the  old  Indian  syringes  and  tubes. 

The  gum  is  now  collected  for  export  in  many 
parts  of  the  world.  South  and  Central  America 
are,  as  they  have  always  been,  the  greatest  produ- 
cers. Some  is  collected  in  Africa,  Java  and  India. 
The  best  comes  from  Para.  However  'carefully 
treated  a great  difference  is  found  in  the  product 
from  different  countries.  The  Brazilian  india  rub- 
ber, known  as  Para,  from  the  port  of  shipment, 
ranks  as  the  best  in  the  market. 

Its  history  as  far  as  recorded,  does  not  go  back  of 
the  last  century.  Le  Oondamine,  who  explored  the 


12 


RUBBER  HAND  STAMP  MAKING 


Amazon  River,  sent  from  South  America  in  1736  to 
the  Institute  de  France,  in  Paris,  the  first  sample  of 
india  rubber  ever  seen  in  Europe.  He  accompanied 
the  sample  with  a communication.  He  said  that 
the  Indians  of  that  country  used  the  gum  in  making 
several  domestic  objects  of  utility,  such  as  vessels, 
bottles,  boots,  waterproof  clothing,  etc.  He  stated 
that  it  was  attacked  and  to  a certain  extent  dis- 
solved by  warm  nut  oil.  In  1751  and  1768  other 
samples  were  received  through  MM.  Fresnau  and 
Maequer,  who  sent  them  to  the  Academy  of  Sci- 
ences, Paris,  from  Cayenne  in  Guiana. 

Although  from  this  period  numerous  experiments 
were  tried  with  the  new  substance  little  of  impor- 
tance was  done  with  it  for  many  years.  Its  first  use 
was  to  rub  out  pencil  marks,  whence  it  derived  its 
name  of  india  rubber.'’^  As  late  as  1820  this  con- 
tinued to  be  its  principal  use. 

An  interesting  reminiscence  of  its  early  history  is 
given  by  Joseph  Priestley,  the  great  English  chemist 
of  the  last  century,  celebrated  as  the  discoverer  of 
oxygen.  In  1770  he  mentioned  the  use  of  the  gum 
for  erasing  pencil  marks,  and  speaks  of  its  cost 
being  three  shillings,  about  seventy  cents,  for  a 
cubical  piece  of  about  half  an  inch.'’'’ 

As  we  have  seen,  its  solubility  was  early  studied. 
In  1761  Herissant  added  turpentine,  ether  and 
^^huile  de  Hippel  to  the  list  of  solvents.  In  1793 
its  solubility  was  utilized  in  France  by  Besson,  who 
made  waterproof  cloth.  In  1797  Johnson  intro- 


AND  THE  MANIPULATION  OF  RUBBER.  13 


duced  for  the  same  manufacture  a solution  in  mixed 
turpentine  and  alcohol. 

The  year  1820  is  the  beginning  of  the  period  of 
its  modern  use  on  a more  extended  scale.  Nadier 
developed  the  methods  of  cutting  it  into  sheets  and 
threads  and  of  weaving  the  latter.  Mackintosh  in 
1823  began  the  manufacture  of  waterproof  cloth, 
using  the  solution  of  the  gum  in  coal  tar  naptha, 
which  was  caused  to  deposit  by  evaporation  a layer 
of  the  gum  upon  a piece  of  cloth  which  was  covered 
by  a second  one.  This  protected  the  wearer  from 
the  gummy  and  sticky  coating  of  raw  india  rubber. 
At  the  best  the  original  Mackintoshes  must  have 
been  very  disagreeable  articles  for  wear. 

In  1825  india  rubber  shoes  of  raw  india  rubber 
were  imported  from  Soutli  America  and  formed  for 
a while  an  important  article  of  commerce. 

In  1839  Charles  Goodyear,  of  Massachusetts,  in- 
vented the  art  of  vulcanizing,  or  combining  india 
rubber  with  sulphur.  It  was  patented  on  June  15, 
1844,  and  covers  only  the  manufacture  of  soft  rub- 
ber. Vulcanite  or  hard  rubber  (whalebone  rubber) 
is  disputed  as  to  its  origin,  its  invention  being 
assigned  by  some  to  Nelson  Goodyear  and  by  others 
to  Austin  G.  Gay,  of  Connecticut.  Goodyear  how- 
ever succeeded  in  obtaining  a patent  on  May  6,  1851. 
Day  obtained  a patent  on  August  10,  1858. 

Vulcanization  is  the  most  important  invention 
ever  made  in  connection  with  india  rubber  and  may 
fairly  rank  as  one  of  the  greatest  discoveries  of  the 


14 


RUBBER  HAND  STAMP  MAKING 


present  century.  It  is  claimed  by  the  English,  an 
inventor  named  Handcock  being  cited  as  the  rival 
of  Charles  Goodyear.  The  latter  inventor  had  as 
an  associate  Nathaniel  Hayward,  who  is  probably 
entitled  to  some  of  the  credit. 

By  vulcanization  india  rubber  loses  susceptibility 
to  heat  and  cold,  becomes  non-adherent,  and  insol- 
uble in  almost  all  substances.  It  is  converted  from 
a comparatively  useless  substance  into  one  of  wide 
applicability. 

The  subject  of  india  rubber  is  so  interesting  in  its 
theoretical  as  well  as  practical  bearings  that  it 
seems  impossible  that  those  who  are  workers  in  it 
should  not  feel  an  interest  in  its  natural  history.  , 
For  such  readers  the  chapter  on  the  natural  history 
and  collection  of  india  rubber  has  been  written. 
As  it  is  a product  of  widely  separated  lands  on  both 
hemispheres,  and  as  it  is  yielded  by  an  immense 
number  of  plants,  it  is  impossible  in  the  limits  of  a 
chapter  to  give  a full  outline  of  its  natural  history. 

The  chapter  in  question  is,  therefore,  with  this 
apology,  inserted  where  it  belongs,  near  the  begin- 
ning of  the  book.  Those  who  are  entirely  practical 
may  pass  it  over.  There  is  no  doubt  that  the  few 
minutes  necessary  for  its  perusal  will  be  bestowed 
upon  it  by  some. 


CHAPTER  II. 


THE  NATURAL  HISTORY  AND  COLLECTION  OF  INDIA 
RUBBER. 

African  india  rubber  is  mostly  exported  from 
the  west  coast.  The  belt  of  country  producing  it 
extends  nearly  across  the  continent.  Those  who  are 
familiar  with  the  india  rubber  plants  of  our  conser- 
vatories are  apt  to  think  of  the  gum  as  the  product 
of  trees,  but  in  Africa  it  is  largely  yielded  by  climb- 
ing plants  of  very  numerous  varieties,  belonging 
generally  to  the  Landolphia  species.  It  is  collected 
by  the  natives  by  careless  or  desultory  methods, 
probably  less  advanced  than  the  ways  followed  by 
the  South  Americans.  Possibly  its  marked  inferior- 
ity may  be  partly  attributed  to  this.  It  is  also  sup- 
posed by  many  that,  were  the  gathering  restricted 
to.  the  vine  producing  the  best  gum,  better  results 
would  follow.  As  it  is  now  all  gums  are  mixed 
indiscriminately.  African  gum  is  of  very  inferior 
quality. 

The  African  india  rubber  vines  grow  often  in 
dark  moist  ravines,  where  no  valuable  product  other 
than  themselves  could  be  cultivated.  They  are 
entirely  wild.  The  vines  when  cut  exude  an  abun- 


16 


RUBBER  HAND  STAMP  MAKING 


dance  of  sap,  which  differs  from  the  South  Amer- 
ican product  in  its  quickness  of  coagulation.  As  it 
escapes  from  the  wound  it  at  once  solidifies  and  pre- 
vents the  further  escape  of  juice.  The  negroes  are 
said  to  employ  the  following  highly  original  method 
of  collecting  it.  They  make  long*  gashes  in  the 
bark.  As  fast  as  the  milky  juice  comes  out  they 
wipe  it  off  with  their  fingers  and  wipe  these  in  turn 
ou  their  arms,  shoulders,  and  body.  In  this  way 
they  form  a thick  covering  of  inspissated  juice  or 
caoutchouc  over  the  upper  part  of  their  body. 
This  from  time  to  time  is  removed  by  peeling.  It 
is  then  said  to  be  cut  up  and  boiled  in  water.  This 
is  one  account.  According  to  others  the  natives 
remove  a large  piece  of  bark,  so  that  the  juice  runs 
out  and  is  collected  in  holes  in  the  earth  or  on 
leaves.  Wooden  vessels  are  said  to  be  used  else- 
where. Sometimes  the  juice  is  said  to  be  collected 
upon  the  arms,  the  dried  caoutciiouc  coming  off  in 
the  shape  of  tubes.  A clew  to  the  inferiority  of 
African  india  rubber  is  afforded  by  the  statement 
that  too  deep  a cut  liberates  a gum  which  deterior- 
ates the  regular  product  if  it  mixes  with  it.  The 
drying  of  the  gum  is  thought  to  have  much  to  do 
with  its  quality  and  it  is  highly  probable  that  this 
affects  the  African  product.  Some  samples  seem  to 
be  partly  decomposed  they  are  so  highly  offensive  in 
odor.  The  South  American  rubber  is  often  dried 
in  thin  layers,  one  over  the  other,  by  a smoky  fire, 
which  may  have  an  antiseptic  effect  upon  the  newly 


AND  THE  3IANIPULATI0N  OF  RUBBER.  17 


coagulated  caoutchouc.  ]^o  such  process  as  far  as 
known  is  used  in  Africa. 

The  African  india  rubber  appears  under  different 
names  in  commerce.  Trom  the  Congo  region  lumps 
of  no  particular  sliape  called  knuckles  ; from 
Sierra  Leone  smooth  lumps^  ‘Aiegro-heads/^  and 

balls  made  up  of  small  scrap  ; from  the  Portu- 
guese ports  thimbles/’  nuts/'’  and  negro- 
heads;  from  the  gaboon  tongues;  and  from 
Liberia  balls  are  received.'’'’  It  is  all  character- 
ized by  great  adhesiveness  and  low  elasticity. 

From  Assam,  Java,  Penang,  and  Rangoon  there 
is  considerable  gum  exported.  It  is  supposed  to  be 
the  product  of  trees  of  the  ficus  species,  in  all  these 
places,  as  it  is  known  to  be  in  Java  and  Assam. 
In  the  latter  place  rigid  restrictions  are  imposed  as 
far  as  possible  upon  the  gathering.  In  the  case  of 
wild  trees  scattered  through  the  forest  the  carrying 
out  of  these  restrictions  is  not  practicable.  The 
trees  are  cut  with  knives  in  long  incisions  through 
the  bark  and  the  juice  is  collected  in  holes  dug  in 
the  ground,  or  often  in  leaves  wrapped  up  into  a 
conical  form,  somewhat  as  grocers  form  their  wrap- 
ping paper  into  cornucopia  shape  for  holding 
sugar,  etc. 

It  has  seemed  reasonably  certain  that  the  india 
rubber  producing  plants  might  be  cultivated  with 
profit,  and  it  is  as  certainly  to  be  feared  that 
without  sucli  cultivation  they  will  become  extinct. 
Lfforts  have  been  made  in  the  direction  of  raising 


18 


BUBBER  HAND  STAMP  MAKING 


them  artificially  but  without  much  success.  In 
Assam  numerous  experiments  have  been  made  to 
propagate  the  india  rubber  bearing  ficus  tree. 

A good  instance  of  the  ill  effects  of  carelessness 
in  the  original  gathering  of  the  crop  is  afforded 
by  the  Bornese  collectors.  The  source  of  Borneo 
india  rubber  is  a variety  of  creepers.  These  are  cut 
down  and  divided  into  short  sections  from  a few 
inches  to  a yard  in  length.  The  sap  oozes  out  from 
the  ends.  To  accelerate  its  escape  the  pieces  are 
sometimes  heated  at  one  end.  It  is  coagulated  by 
salt  water.  Sometimes  a salt  called  nipa  salt,  ob- 
tained by  burning  a certain  plant  {nipa  fruticans'),  is 
used  for  the  purpose.  In  either  case  it  is  coagulated 


Tree  Felled  for  Collection  of  India  Rubber. 

into  rough  balls  and  masses.  These  masses  are 
heavily  charged  with  the  salt  water,  often  contain- 
ing as  much  as  fifty  per  cent.,  and  rarely  much  less 
than  twenty  per  cent. 

Central  America  and  Panama  are  great  producers 
of  the  gum.  In  Panama  the  custom  of  felling  the 


AND  THE  MANIPULATION  OF  PUBDEIL  19 


trees  is  often  adopted.  In  this  case  grooves  are  cut 
around  the  prostrate  trunks  and  under  each  groove 
as  the  trunk  lies  on  the  ground  a vessel  is  placed  to 
collect  the  sap.  Its  coagulation  is  often  effected  by 
♦leaving  it  for  a couple  of  weeks  standing  at  rest  in  a 
hole,  excavated  on  the  surface  of  the  ground,  and 
covered  over  with  leaves.  The  caoutchouc  sepa- 
rates under  these  conditions.  A quicker  method, 
but  one  yielding  an  inferior  product,  is  obtained  by 
adding  to  the  fresh  juice  some  bruised  leaves  of  a 
plant  {ipomma  bona  nox)  which  acts  something 
like  acid  upon  milk,  in  separating  the  desired  solid 
matter  or  caoutchouc.  A jelly  like  accretion  satu- 
rated with  blackish  water  is  thus  obtained.  By 
working  it  together  a blackish  liquid  is  caused  to 
escape,  and  comparatively  pure  gum  is  gradually 
obtained.  As  much  as  one  hundred  pounds  of 
india  rubber  may  be  obtained  from  a single  tree 
where  this  destructive  system  is  employed.  Fur- 
ther north,  where  a better  counsel  has  prevailed,  the 
trees  are  only  tapped,  and  the  india  rubber  hunter 
is  satisfied  if  from  a tree  eighteen  inches  in  diam- 
eter he  obtains  twenty  gallons  of  sap,  giving  fifty 
pounds  of  gum.  Even  where  tapping  is  done  the 
tree  is  often  destroyed  by  carelessness  or  ignor- 
ance. 

Two  systems  are  followed  in  Nicaragua.  The  oper- 
ator ascends  by  a ladder  if  he  has  one,  or  in  any  case 
climbs  as  high  as  he  well  can  and  begins  to  make  a 
long  incision.  Sometimes  he  carries  one  long  straight 


20 


RUBBER  HAND  STAMP  AIAKING 


cut  clear  down  to  the  ground.  This  is  made  the 
starting  point  for  a number  of  side  cuts,  short,  and 
running  diagonally  into  it.  This  is  also  one  of  the 
Brazilian  methods.  The  Nicaraguan  sometimes 
also  makes  two  spiral  incisions,  one  right-handed^ 
and  the  other  left-handed,  crossing  each  other  as 
they  descend  so  as  to  divide  the  surface  of  the  tree 
into  roughly  outlined  diamonds.  In  either  case  the 
juice  flows  down  to  an  iron  spout,  placed  at  the 
bottom  of  the  tree,  which  spout  leads  to  an  iron 
pail.  The  milk  is  gathered  and  passed  through  a 
sieve,  and  coagulated  in  barrels  by  the  ipomcea  plant 
as  before  mentioned.  This  gives  three  grades  of 
rubber.  The  bulk  is  obtained  from  the  barrels  and 
is  called  often  meros;  the  small  lump  which  forms  in 
the  spout  is  rolled  into  a ball  and  called  cabezza; 
the  dried  strips  pulled  out  of  the  cuts  is  of  very 
good  quality  and  is  called  bola  or  huruclia. 

From  Brazil  is  exported  the  famous  Para  india 
rubber.  This  is  of  very  higli  quality,  and  is  greatly 
esteemed  by  all  manufacturers.  No  process  can 
make  a poor  gum  give  a really  good  product.  The 
system  of  gathering  it  varies.  Sometimes  the  tree 
is  cut  into  by  gashes  from  an  axe,  such  gashes  ex- 
tending in  a row  all  around  the  trunk.  Under  each 
gash  a small  clay  cup  is  luted  fast  with  some  fresh 
mixed  clay.  These  collect  from  a tablespoonful  of 
juice  upward,  which  is  collected,  and  the  cups  are 
removed  on  the  same  day.  The  next  day  a second 
row  of  cuts  is  made  below  the  others,  and  the  same 


AND  THE  MANIPULATION  OF  RUBBER.  21 


process  is  repeated.  This  is  continued  until  from  a 
point  as  high  as  a man  can  reach,  down  to  the 
ground  the  tree  is  full  of  cuts.  Sometimes  a gutter 
of  clay  is  found  partly  around  the  trunk  with 
gashes  above  it.  In  other  cases  a vine  is  secured 


around  the  tree  and  a collecting  gutter  is  worked 
with  it  for  a basis. 

The  juic-e  is  coagulated  rn  a smoky  fire.  A bot- 
tomless Jar  is  placed  over  the  fire  and  some  palm 
nuts  are  mixed  with  the  fuel.  The  mould,  which  is 
often  a canoe  paddle,  is  smeared  with  clay  to  pre- 
vent adhesion  and  is  then  heated.  A cup  of  juice 
is  poured  over  it,  and  after  the  excess  has  dropped 
off  it  is  moved  about  rapidly  over  the  smoke  and 


Tree  Tapped  for  India  Rubber. 


'2*2  nUBBER  HAND  STAMP  MAKING 

hot  air  which  ascends  from  the  month  of  the  jar. 
This  series  of  operations  is  repeated  until  the  coat- 
ing is  quite  thick;  it  may  be  as  much  as  five  inches. 
After  solidifying  over  night  it  is  cut  open  and  the 
paddle  or  mould  is  removed.  After  a few  days  dry- 


Indian  Drying  and  Smoking  India  Rubber. 

ing  it  is  sent  to  market.  With  all  the  heating, 
during  which  it  sweats  profusely,  it  still  retains 
fifteen  per  cent,  of  water. 

India  rubber  sap  may  be  coagulated  by  an  aqueous 
solution  of  alum.  The  process  has  been  tried  in 
Brazil,  and  is  used  to  a considerable  extent  in 


AX  I)  THE  MAjYIPULATWX  OF  ElTBBBR.  28 


Pernambuco.  It  was  proposed  by  an  investigator 
named  Stmuss,  and  the  process  is  still  called  by  his 
name.  One  objection  is  that  it  gives  a very  wet 
product,  and  apparently  one  of  inferior  value  to  the 
smoked  gum. 

The  feeling  that  India  rubber  suffers  in  the  gath- 
ering has  been  so  much  felt  that  it  has  been  re- 
cently suggested  that  if  possible  the  uncoagulated 
juice  should  be  exported  to  Europe  there  to  be 
worked  up  from  the  beginning. 


CHAPTER  III. 


PROPERTIES  OF  UKYULCANIZED  AND  VULCANIZED 
INDIA  RUBBER. 

There  are  two  broad  divisions  to  which  all  varie- 
ties of  india  rubber  can  be  assigned — iinviilcanized 
and  vulcanized  rubber.  Speaking  with  a certain 
amount  of  license  it  may  be  said  that  more  proper- 
ties characterize  the  former  than  the  latter.  The 
vulcanized  article  is  very  slightly  affected  by  ordi- 
nary changes  of  temperature,  cannot  to  any  consid- 
erable extent  be  changed  by  heat  short  of  absolute 
destruction  or  decomposition,  cannot  be  united  or 
moulded  except  in  simple  forms,  is  highly  elastic, 
and  is  insoluble  in  almost  every  solvent  for  ordinary 
caoutchouc. 

Unvulcanized  caoutchouc  possesses  very  interest- 
ing and  peculiar  properties.  The  first  part  of  the 
present  chapter  is  devoted  to  this  substance.  Those 
who  have  never  seen  the  crude  gum  as  imported  are 
familiar  with  the  article  almost  pure  in  the  form  of 
sheet  rubber  and  black  rubber  articles  generally. 
These  are  of  nearly  pure  caoutchouc,  though  recently 
the  tendency  is  to  vulcanize  them  to  a considerable 
degree. 


AND  THE  MANIPULATION  OF  RUBBER.  25 


A piece  of  pure  gum  containing  no  combined 
sulphur,  iodine,  or  other  vulcanizing  constituent 
will  be  found  to  exhibit  a very  striking  peculiarity. 
Two  freshly  cut  surfaces  when  placed  in  contact 
will  adhere.  This  is  not  in  consequence  of  any 
viscous  or  sticky  coating.  When  india  rubber  is 
cut  tlie  surface  is  perfectly  dry  and  non-adherent 
except  to  itself. 

The  writer  once  had  this  property  of  adhesion 
brought  strongly  to  his  attention.  In  some  analyt- 
ical investigations  of  coal  gas  he  had  proposed  to 
use  finely  divided  india  rubber  as  an  absorbent  of 
sulphur.  This  constituent  it  absorbs  from  gas,  and 
it  seemed  that  a basis  for  a quantitative  determina- 
tion of  sulphur  might  be  found  in  such  property. 
Accordingly  some  raw  india  rubber  was  procured 
and  with  some  trouble  was  cut  up  into  'little  pieces 
which  were  put  into  a bottle.  A day  or  two  after- 
wards the  pieces  united  wherever  they  were  in  con- 
tact, and  an  irregular  cavernous  lump  was  the 
result.  This  involved  no  melting  or  softening  or 
change  of  shape.  Each  little  piece  was  there  intact 
and  distinct  but  firmly  attached  to  its  neighbors. 

The  analogy  of  this  action  is  seen  in  lead.  Two 
fresh  surfaces  brought  together,  preferably  with  a 
twisting  or  wrenching  pressure,  adhere  quite  firmly. 
The  adherence  of  india  rubber  and  of  lead  each  to 
itself  is  often  exhibited  by  physical  lecturers  as  an 
illustration  of  cohesion.  The  cohesion  of  india 
rubber  is  however  far  more  perfect  than  that  of 


26 


RUBBER  HAND  STAMP  MAKING 


lead^  probably  because  of  its  comparatively  great 
resistance  to  oxidation,  and  because,  owing  to  its 
elasticity  larger  areas  can  be  brought  in  contact. 
Comparatively  great  though  this  resistance  to  oxi- 
dation is,  oxygen,  especially  in  the  allotropic  modi- 
fication known  as  ozone,  may  act  quite  powerfully 
on  the  gum.  Sunlight  also  can  affect  it  injuri- 
ously. 

A more  familiar  illustration  of  the  uniting  of  two 
pieces  of  the  same  material  is  seen  in  the  welding 
of  iron.  The  blacksmith  heats  two  pieces  of  iron 
until  they  are  nearly  white  hot  and  are  pasty  in 
consistency.  On  placing  them  in  contact  and  ham- 
mering to  force  them  together  they  unite  so  firmly 
as  to  be  practically  one.  It  is  necessary  that  the 
surfaces  of  clean  metal  should  be  brought  together. 
If  the  pressure  induced  by  the  hammering  is  insuf- 
ficient to  bring  this  about,  a flux  is  added  which 
dissolves  the  oxide  and  causes  the  metal  to  come  in 
contact  with  metal  and  to  weld.  The  analogy  with 
india  rubber  in  its  cohesive  action  is  evident.  Sur- 
faces long  exposed  or  which  are  dusty  do  not  cohere. 
The  relegation  of  ice  is  similar  in  effect. 

The  cohesion  of  india  rubber  is  important  and 
should  be  thoroughly  appreciated.  It  is  not  saying 
too  much  to  assert  that  the  entire  treatment  of  the 
raw  gum  depends  upon  this  interesting  property. 
The  great  lumps  of  gum  are  torn  to  pieces  and 
washed 'free  from  gravel  and  dirt  without  going  to 
powder,  because  owing  to  their  elasticity  they,  yield 


AND  THE  MANIPULATION  OF  BUB  BEE.  27 


and  as  fast  as  torn  apart  the  ]Dieces  tend  to  reunite. 
Again  india  rubber  is  mixed  with  pigments  and  vul- 
canizing reagents  by  a method  practically  one  of 
grinding  or  masticating,  but  the  material  while  it 
changes  its  shape,  and  by  the  admixture  of  the  va- 
rious ingredients  becomes  less  strong  or  easier  torn, 
still  remains  intact,  as  it  welds  together  or  coheres 
as  fast  as  disintegrated. 

As  regards  its  chemical  constitution  the  sap  of  a 
Para  rubber  tree  has  been  analyzed  with  the  follow- 
ing general  results:  (Faraday). 


Caoutchouc 80.70 

Albuminous,  extractive,  and  saline  matter,  etc 12.93 

Water 56.37 


100.00 

Its  specific  gravity  is  1.012. 

Caoutchouc  itself  or  raw  india  rubber  is  a mixture 
of  several  hydrocarbons  of  the  following  composi- 
tion in  general: 


Carbon.... 87.5 

Hydrogen 12.5 


100.0 

Its  specific  gravity  is  from  .912  to  .942. 

The  hydrocarbons  composing  it  are  isomeric  or 
polymeric  with  turpentine.  This  fact  brings  it  well 
within  the  range  of  familiar  vegetable  products. 
.\s  will  be  seen  the  products  of  its  distillation  fall 
among  the  same  polymers  and  isomers. 


28 


RUBBER  HAND  STAMP  MAKING 


When  pure  it  is  nearly  colorless,  the  dark  color 
being  due  to  impurities.  In  thin  sheets  it  is  almost 
or  quite  transparent.  It  burns  readily,  and  with  a 
very  luminous,  smoky  flame,  as  might  have  been 
anticipated  from  its  composition.  The  action  of 
heat  and  cold  on  it  is  dependent  on  the  degree  of 
the  temperature.  At  ordinary  temperature  it  is 
elastic  and  firm.  It  can  be  stretched  and  will  re- 
turn almost  to  its  original  size  when  released  from 
tension.  Yet  the  return  to  its  shape  is  so  liable 
to  be  incomplete,  especially  after  long  sustained 
stretching,  that  pure  unvulcanized  india  rubber  is 
considered  imperfectly  elastic. 

Any  elasticity  it  possesses  is  principally  elasticity 
of  shape  as  distinguished  from  elasticity  of  volume. 
In  other  words  when  pressed  or  stretched  it  may 
change  shape  to  a great  extent  but  hardly  change 
its  volume  at  all.  A cube  of  2^4  inches  under  a 
weight  of  200  tons  lost  1-10  of  its  volume  only. 
This  is  largely  due  to  the  fact  that  it  represents  an 
approximately  solid  body,  or  one  destitute  of  consid- 
erable physical  pores.  Solids  and  liquids  are  very 
slightly  compressible.  Whatever  degree  of  com- 
pressibility caoutchouc  possesses  is  due  principally 
to  its  minute  pores. 

If  the  temperature  is  reduced  to  the  freezing 
point  of  water  a piece  of  raw  india  rubber  becomes 
rigid  and  stiff.  On  application  of  heat  it  returns  to 
its  former  pliable  condition.  The  same  return  to 
flexibility  may  be  brought  about  by  stretching  it 


AND  THE  MANIPULATION  OF  BUBBER.  29 


mechanicall}^  This  may  be  rather  a fallacy. 
Stretching  iiidia  rubber  warms  it,  so  that  in  this 
mechanically  imparted  rise  of  temperature  we  may 
find  at  least  a probable  cause  of  the  softening. 

If  the  temperature  is  raised  several  effects  are 
produced,  according  to  circumstances.  A piece 
which  has  been  stretched  and  held  stretched,  has  its 
tension  increased  by  a degree  of  heat  considerably 
less  than  that  of  boiling  water.  Some  offer  the 
theory  that  it  contains  air  enclosed  in  its  pores 
which,  expanding,  produces  this  effect.  As  the 
boiling  point  is  reached  the  material  softens  and 
becomes  somewhat  plastic,  so  that  it  can  be  moulded 
into  shape  to  a considerable  extent  and  stretched  to 
threads  of  great  fineness.  Its  elasticity  also  disap- 
pears as  the  heat  is  maintained.  These  effects  in- 
crease in  extent  up  to  a heat  of  248°  F.  (120'^  0.). 
The  return  to  its  original  state  is  not  immediate 
however.  Some  time  is  required  before  the  reduc- 
tion of  temperature  will  have  full  effect. 

If  now  a still  higher  degree  of  heat  is  applied, 
392°  F.  (200°  C.)  the  india  rubber  softens  to  a 
viscous  body,  or  melts.  From  this  state  it  cannot 
be  restored.  It  remains  permanently  “burned^'’  or 
melted  whatever  is  done  to  it.  Some  attempt  at 
hardening  may  be  made  by  the  use  of  vulcanizing 
chemicals,  but  the  result  will  be  very  imperfect. 

A further  increase  of  heat  brings  about  a destruc- 
tive distillation.  India  rubber  treated  in  a retort  to 
a heat  exceeding  400°  F.  (204°  C.)  evolves  volatile 


30 


RUBBEB  HAND  STAMP  MAKING 


hydrocarbons  of  oily  consistency,  and  it  distills 
almost  completely,  a small  residue  of  gummy  mat- 
ter or  of  coke  if  the  final  heat  has  been  pushed  far 
enough  being  left.  The  distillate  is  called  caout- 
choucin.  According  to  Mr.  Greville  Williams  it  con- 
sists of  two  polymeric  hydrocarbons  : one,  caout- 
chin  CioHie,  boiling  point  340°  F.  (171°  C.);  the 
other,  isoprene  CsHg  (in  formula  equal  to  one-half 
of  caoutchin),  boiling  point  99°  F.  (37°  0.)..  The 
mixture  has  a strong  naptha-like  odor  and  has  won 
considerable  reputation  as  being  the  best  solvent  for 
India  rubber.  How  far  it  deserves  its  reputation  is 
a matter  open  to  discussion. 

The  solution  of  india  rubber  like  its  fusion  is  a 
vexed  point.  There  is  little  question  that  it  can  be 
dissolved  by  proper  treatment.  Usually  naptha, 
carbon  disulphide  or  benzole  are  used  as  solvents,  the 
choice  being  guided  by  motives  of  cheapness  and 
efficiency. 

It  is  worthy  of  remark  that  the  formula  given  for 
caoutchoucin  is  the  same  as  that  of  the  principal 
constituent  of  oil  of  turpentine,  and  that  the  latter  is 
often  recommended  as  a solvent.  Turpentine  is 
slightly  more  volatile  than  caoutchoucin,  its  boiling 
point  being  322°  F.  (161°  C.)  Other  hydrocarbons 
have  been  recognized  in  the  distillate  by  Bou- 
chardat,  Himly  and  G.  Williams,  varying  in  boiling 
point  from  32°  F.  (0°  C.)  to  599°  F.  (315°  C.),  and  in 
specific  gravity  from  0.630  to  0.921. 

Although  it  has  been  spoken  of  as  approximately 


AND  THE  MANIPULATION  OF  BUBBEB.  81 


solid  it  does  possess  microscopic  pores,  to  which  its 
limited  amount  of  elasticity  of  volume  is  mostly 
due.  Thus  it  is  found  to  absorb  water,  in  which  it 
is  quite  insoluble.  As  it  does  this  it  acts  like  a dry 
sponge  and  increases  in  volume  a little,  owing  to 
dilation  of  these  minute  pores.  The  water  absorbed 
may  be  as  much  as  18.7  to  26.4  per  cent,  with  an  in- 
crease of  volume  of  the  gum  of  tUo  to  When 

it  has  once  absorbed  water  it  is  very  hard  to  get  rid 
of  it.  Although  the  minute  surface  orifices  commu- 
nicate with  the  entire  system  of  capillary  vessels 
and  pores,  the  surface  pores  on  drying  contract  and 
seal  up  the  absorbed  water  within  the  mass.  This 
is  a clew  to  the  impracticability  of  the  gatherer  ship- 
ping dry  rubber,  and  to  the  great  difficulty  the 
manufacturer  experiences  in  drying  his  washed  and 
sheeted  stock  before  working  it  up  by  masticating 
or  mixing  and  curing. 

By  proper  manipulation  caoutchouc  may  be  made 
inelastic.  This  can  be  done  by  the  freezing  process 
or  by  keeping  it  stretched  for  two  or  three  weeks. 
In  this  way  threads  can  be  made  to  extend  and  to 
remain  extended  to  seven  or  eight  times  their  orig- 
inal length.  They  can  then  be  woven  into  a fabric. 
On  gentle  heating  their  original  elasticity  reappears 
and  they  contract.  In  this  way  fluted  braids  can  be 
made  which  will  have  a high  capacity  for  stretch- 
ing. 

The  solution  of  caoutchouc  is  difficult  often  to 
bring  about.  We  have  seen  that  in  water  it  swells 


32 


RUBBER  HAND  STAMP  MAKING 


a little  without  dissolving.  In  benzole  it  does  the 
same,  but  swells  to  a greater  extent,  to  125  times  its 
original  volume  or  even  more.  Some  authorities 
( Watts)  go  so  far  as  to  assert  that  no  solvent  com- 
pletely dissolves  it.  Acting  on  it  repeatedly  with 
benzole  or  other  solvent  and  taking  care  not  to 
break  up  the  swelled  mass,  from  49  to  60  per  cent, 
of  soluble  matter  can  be  extracted.  On  evaporation 
this  is  deposited  as  a ductile  adherent  film.  The 
swelled  up  residue  which  remains  undissolved  is 
assumed  to  be  the  constituent  giving  strength  and 
elasticity,  and  is  only  sparingly  soluble.  If  the 
gum  is  masticated  or  kneaded  at  the  temperature  of 
boiling  water  a change  occurs  not  well  understood, 
by  which  its  solubility  is  greatly  increased.  • As 
solvents  many  liquids  have  been  named.  Oil  of 
turpentine,  caoutchoucin,  coal-tar,  naptha,  benzole, 
petroleum-naptha,  coal-tar-naptha,  anhydrous  ether, 
many  essential  oils,  chloroform,  bisulphide  of  car- 
bon, pure,  or  mixed  with  seven  or  eight  per  cent,  of 
alcohol,  are  among  the  solvents  recommended.  A 
mixture  of  fifty  parts  of  benzole  and  seventy  parts 
of  rectified  turpentine  has  been  given  as  a solvent 
for  twenty-six  parts  of  the  gum.  Mastication  be- 
fore or  after  immersion  in  the  solvent  is  to  be 
advised.  More  will  be  said  on  this  subject  in  a 
succeeding  chapter. 

Vulcanized  india  rubber  is  unaffected  by  changes 
of  temperature  within  ordinary  range.  It  softens  a 
little  on  heating.  Even  hard  vulcanite  when  heated 


AND  THE  2IANIPULATI0N  OF  RUBBER.  33 


can  be  bent  and  will  retain  the  bend  on  cooling. 
It  is  exceedingly  elastic  witli  elasticity  of  shape  but 
far  less  compressible  as  regards  absolute  change  of 
volume  than  the  raw  gum.  It  melts  at  392°  F. 
(200°  C.)  It  cannot  be  made  to  cohere,  and  no 
cement  has  yet  been  discovered  that  will  satisfac- 
torily unite  two  surfaces.  It  is  unaffected  by  light, 
by  ordinary  acids  and  rubber  solvents.  In  contact 
with  the  latter  solvents  it  swells  sometimes  to  nine 
times  its  original  volume,  but  on  heating  returns  to 
its  original  volume  and  shape.  Of  water  it  will 
absorb  no  more  than  four  per  cent,  and  often  much 
less.  If  it  is  maintained  at  a high  temperature 
266°  to  302°  F.  (130°  to  150°  C.)  for  a long  time  it 
gradually  loses  its  flexibility,  especially  if  in  con- 
tact with  metals.  Often  the  escape  of  sulphuretted 
hydrogen  may  be  observed  under  these  conditions. 
A small  admixture  of  coal  tar  operates  to  prevent 
this  action. 

Its  composition  and  specific  gravity  vary  widely 
as  the  most  varied  mixtures  are  added  by  the  manu- 
facturer. Its  relation  of  carbon  to  hydrogen  is 
unaffected  by  the  mixtures  added.  While  it  may 
contain  twenty  per  cent,  or  more  of  sulphur  it  is 
believed  that  but  a very  small  quantity  is  combined 
with  it,  although  the  excess  of  sulphur  or  some 
equivalent,  such  as  sulphide  of  antimony  is  essen- 
tial to  vulcanization.  The  combined  sulphur  is 
from  one  to  two  per  cent.  Some  or  all  of  the  ex- 
cess of  sulphur  is  mechanically  retained,  and  as  the 


34 


BUBBER  HAND  STAMP  MAKING 


rubber  in  ordinary  use  is  worked  about^  keeps  escap- 
ing and  forms  a whitish  dust  upon  the  surface.  By 
treatment  with  alkali  some  of  the  excess  of  sulphur 
can  be  removed  when  the  rubber  acquires  the  jjower 
of  absorbing  a little  more  water,  up  to  six  and  four- 
tenths  per  cent. 

Boiling  oil  of  turpentine  is  given  as  its  solvent. 


CHAPTER  lY. 


THE  MANUFACTUKE  OF  MASTICATED,  MIXED  SHEET, 
AFTD  VULCANIZED  INDIA  EUBBER. 

The  manufacture  of  India  rubber  relates  to  the 
production  of  two  principal  products.  One  is  mas- 
ticated unvulcanized  sheet  and  thread  rubber;  the 
other  is  unmasticated  mixed  and  cured  rubber, 
otherwise  vulcanized  rubber.  For  the  purposes  of 
the  rubber-stamp  maker  an  intermediate  product  is 
required,  namely,  unmasticated  mixed  sheet  which 
is  uncured.  This  is  really  incompletely  vulcanized 
india  rubber. 

It  will  be  evident  from  the  description  to  come 
that  it  is  not  advisable  for  any  one  without  consider- 
able apparatus  to  attempt  to  clean  and  to  wash  to 
sheet  to  masticate,  or  to  mix  india  rubber. 
These  operations  are  best  accomplished  in  the  fac- 
tories. The  partially  vulcanized  mixed  sheet 
or  the  pure  masticated  article  are  regular  articles  of 
commerce.  Yet  a full  insight  into  the  manipula- 
tion of  india  rubber  can  only  be  obtained  by  under- 
standing its  treatment  from  the  gum  up  to  the  two 
separate  lines  of  products  we  have  indicated. 

A third  type  of  product  is  coated  tissue,  such  as 


86  BUBBEB  HAND  STAMP  MAKING 

Mackintosh.  This  really  is  a sequence  of  one  of 
the  other  two  processes  and  a few  words  will  be  said 
of  it  in  concluding  the  chapter. 

As  the  caoutchouc  is  received’  by  the  manufac- 
turer it  appears  an  utterly  intractable  mass.  It 
occurs  in  lumps  of  every  size,  varying  in  color  and 
odor,  and  very  tough  but  elastic.  In  virtue  how- 
ever of  the  properties  already  described,  its  power  of 
cohering  when  cut,  and  its  softening  when  heated, 
it  becomes  amenable  to  treatment. 

It  is  to  some  extent  received  in  such  assorted 
condition  as  to  secure  even  grades,  and  then  each 
grade  may  be  washed  by  itself.  It  is  thrown  into 
water  which  is  in  many  cases  kept  at  the  boiling 
point  by  steam-heat  and  left  there  for  some  hours. 
It  absorbs  some  water  and  also  softens.  Some  gum 
is  so  soft  that  it  will  not  stand  hot  water.  For  such 
the  water  is  kept  cold.  The  purer  gum  floats;  such 
pieces  as  have  stones,  dirt,  iron,  etc.  in  them,  per- 
haps placed  there  purposely  from  fraudulent  motives, 
sink  and  can  be  picked  out  for  separate  treatment. 

The  lumps  are  next  cut  up.  A revolving  circular 
knife  driven  by  power  is  often  used,  and  sometimes 
an  ordinary  knife  is  adopted.  ^ At  this  part  of  the 
operation  there  is  frequently  meed  for  sorting,  as  the 
grades  received  may  have  inferior  pieces  mixed  with 
the  good.  The  cutting  is  mainly  to  secure  good 
grading,  and  to  remove  concealed  impurities.  The 
gum  then  goes  to  the  Avashing  rollers,  called  the 
washer  and  sheeter.  (See  cut,  p.  37.) 


AND  THE  MANIPULATION  OF  RUBBER.  37 


These  are  heavy  corrugated  rolls  made  very  short, 
0-18  inches  in  length,  to  prevent  springiiig.  They 
are  grooved  or  corrugated  and  have  a screw  adjust- 
ment for  regulating  their  distance  apart.  They 
are  geared  together  so  as  to  work  in  corresponding 
directions,  like  a clothes  wringer  or  a rolling  mill 
of  any  kind.  The  pieces  of  gum  are  fed  into  the 


Washer  and  Sheeter. 


rolls  and  are  drawn  between  and  through  them. 
The  friction  tends  to  heat  the  gum.  To  prevent 
this  and  also  to  effect  the  washing,  a supply  of 
water,  either  hot  or  cold,  is  kept  playing  upon  the 
mass.  This  dissolves  out  all  soluble  matter  and 
washes  away  mechanically  the  chips,  dirt,  etc. 
which  may  be  present.  The  whole  operation  is  one 
of  main  force.  The  caoutchouc  is  torn  and  dis- 
tended and  delivered  as  a rough  perforated  sheet. 
It  is  passed  repeatedly  through  the  machine,  the 
rollers  being  gradually  brought  closer  together,  or 
else  different  sets  of  rolls  are  used,  set  to  different 


38 


miBBEB  HANB  STAMP  AIAKING 


degrees  of  fineness.  The  wash  water  passes  through 
a screen  which  catches  any  small  detached  frag- 
ments of  gum. 

Other  types  of  machines  have  been  introduced; 
the  above  is  a representative  form. 

The  rough  sheets  must  now  be  perfectly  dried,  as 
water  impairs  the  final  product.  This  is  done  in 
drying  rooms  by  steam  heat,  generally,  at  a temper- 
ature of  about  90°  F.  (32°  0.)  The  windows,  if 
there  are  any,  are  painted  to  exclude  sunlight, which 
operates  to  deteriorate  raw  gum.  When  absolutely 
dry  the  caoutchouc  is  removed  and  stacked  away 
for  use. 


To  prepare  pure  gum  for  the  manufacture  of 
sheet  rubber  and  as  a starting  point  for  many  other 
preparations,  the  india  rubber  is  masticated  in 


AND  THE  MANIPULATION  OF  RUBBER.  39 


special  apparatus.  The  machine  consists  of  a fixed 
cylinder  within  which  is  a corrugated  roller  set 
eccentrically  and  rotated  by  power.  The  perfectly 
dry  sheets  in  the  masticator  are  pressed  and  rolled 
and  ground  and  produce  a mass  of  even  consistency. 
Here  the  welding  or  cohering  action  again  appears 
in  its  fullest  development.  The  perfect  dryness  of 
the  mass  enables  it  to  keep  reuniting  as  fast  as 
divided.  The  action  is  assisted  by  the  heat  gener- 
ated, which  is  not  inconsiderable.  Sometimes  the 
caoutchouc  is  warmed  before  introduction,  and 
sometimes  the  roller  is  heated  by  passing  steam 
through  it. 


The  masticating  machine  the  French  pictur- 
esquely term  the  wolf  (loup)  or  devil  {dtahle).  It  is 
given  from  sixty  to  one  hundred  turns  a minute, 
and  a machine  large  enough  to  treat  fifty  pounds  of 


4o 


EUBBER  HAND  STAMP  MAKING 


gum  in  a charge,  requires  five  horse-power  to  drive 
it.  In  it  the  sheeted  gum  is  ultimately  brought  to 
the  state  of  a perfectly  homogeneous  dark  brown 
translucent  mass. 

The  masticated  rubber  is  peculiarly  amenable  to 
mechanical  and  chemical  treatment.  It  can  be 
shaped  by  heat  and  pressure,  and  it  is  the  most 
soluble  form  and  is  used  for  making  cement  and 
solution,  and  is  moulded  into  blocks  for  the  manu- 
facture of  sheet  and  thread  rubber.  In  the  process 
neutral  body  pigments,  such  as  oxide  of  zinc,  or  sol- 
uble transparent  ones,  such  as  alkanine  may  be  intro- 
duced; easily  decomposed  matter  cannot  be  incorpo- 
rated on  account  of  the  heat. 

In  all  these  machines  special  provision  is  made 
to  prevent  any  oil  from  getting  into  the  gum. 
There  is  no  greater  enemy  to  india  rubber  than  oil 
or  fats  of  any  description.  The  flanges  in  the  mas- 
ticator that  roll  just  inside  the  bearing  are  for  this 
purpose. 

Sheet  rubber  is  made  from  the  blocks  of  masti- 
cated gum  by  slicing.  A machine  is  used  for  the 
purpose  which  carries  a knife  which  works  back 
and  forth  in  the  direction  of  its  length  at  high 
speed,  making  two  thousand  cuts  a minute.  The 
knife  is  kept  wet  by  a stream  of  water,  and  about 
sixty  cuts  are  made  per  inch.  In  many  articles 
made  from  this  sheet  the  marks  of  the  cuts  can  be 
seen  as  a fine  ribbing.  The  appearance  is  familiar 
to  many  readers. 


AND  THE  3IANIPULAriON  OF  BVEBER,  4l 


The  sheet  is  often  out  from  rectangular  blocks, 
but  cylindrical  blocks  are  also  used.  The  latter  are 
rotated  in  front  of  the  knife  edge  and  a long,  con- 
tinuous sheet  can  thus  be  obtained. 

The  sheet  rubber  can  be  cut  into  threads  on  web- 
bing and  braid.  Everyone  has  noticed  that  these 
threads  are  usually  square.  The  method  of  prepa- 
ration accounts  for  it.  Vulcanized  sheet  is  now 
almost  universally  used  for  threads. 

Round  threads  however  can  be  made  by  forcing 
softened  or  partly  dissolved  gum  through  a die. 

It  is  from  unvulcanized  masticated  sheet  that 
toy  balloons,  tobacco  pouches,  etc.,  are  made.  It  is 
the  starting  point  for  india  rubber  bands.  For  the 
usual  form  of  the  latter  article  the  sheet  is  cemented 
into  a long  tube  which  is  afterwards  cut  transversely, 
giving  bands  of  any  desired  width.  To  make  any 
of  these  articles  satisfactory  vulcanization  is  imper- 
ative. Unvulcanized  rubber  for  many  years  was 
used,  but  it  is  now  completely  displaced  by  the 
vulcanized  product.  Sheet  rubber  is  made  as  above; 
is  vulcanized  by  some  of  the  absorption  processes 
described  in  the  chapter  on  vulcanization. 

We  now  come  to  the  second  product:  regularly 
mixed  and  cured  rubber.  Its  starting  point  is 
the  washed  india  rubber  from  the  washer  and 
sheeter. 

We  have  seen  that  the  pure  gum  or  caoutchouc  is 
very  sensitive  to  changes  of  temperature.  At  the 
freezing  point  of  water  it  is  hard  and  rigid,  and  at 


42 


RUBBER  HAND  STAMP  MAKING 


the  boiling  point  is  like  putty  in  consistency. 
There  are  several  substances  which  can  be  made  to 
combine  with  the  gum  and  which  remove  from  it 
this  susceptibility  to  change  of  temperature.  The 
process  of  effecting  this  combination  is  called  vul- 
canization, and  the  product  is  called  vulcanized 
india  rubber.  Sulphur  is  the  agent  most  generally 
employed. 

In  the  factory  the  normal  vulcanization  is  carried 
out  in  two  steps,  mixing  and  curing.  The  washed 
sheet  india  rubber  which  has  not  been  masticated 
and  which  must  be  perfectly  dry  is  the  starting 


Making  Mixed  Rubber. 


point,  and  the  mixing  rolls  shown  in  the  cuts  are  the 
mechanism  for  carrying  out  the  first  step.  These 
are  a pair  of  powerful  rollers  which  are  geared  so  as 
to  work  like  ordinary  rolls,  except  that  one  revolves 


AXD  THE  HAXIPULATIOX  OF  RUBBER.  43 


about  three  times  as  fast  as  the  other.  Tliey  are 
heated  by  steam,  which  is  introduced  inside  of 
them.  The  sheet  is  first  passed  through  them  a 
few  times  to  secure  its  softness,  and  then  the  opera- 
tive begins  to  sprinkle  sulphur  upon  it  as  it  enters 
the  rolls.  This  is  continued,  the  rubber  j)assing  and 
repassing  until  perfect  incorporation  is  secured. 
About  ten  per  cent,  of  sulphur  is  added,  and  a work- 
man can  take  care  of  thirty  pounds  at  a time. 

This  material  is  incompletely  vulcanized.  It  is 
in  its  present  condition  very  amenable  to  heat  and 
is  ready  for  any  moulding  process.  Generally  it  is 
rolled  out  or  calendered into  sheets  of  different 
thickness  from  which  articles  are  made  in  moulds 
by  curing. 

These  sheets  are  of  especial  interest  to  the  reader 
as  they  are  the  material  from  which  most  small  arti- 
cles are  made,  including  rubber  stamps. 

This  rolling  of  the  mixed  india  rubber  into  sheets 
of  definite  thickness  is  done  by  special  calendering 
rolls.  The  product  is  termed  mixed  sheet. 

In  the  mixing  rolls  the  incor|)oration  of  other 
material  is  often  brought  about.  Zinc  white,  lead 
sulphide,  antimony  sulphide,  chalk,  clay,  talc, 
barium  sulphate,  plaster  of  paris,  zinc  sulphide, 
lead  sulphate,  white  lead,  oxides  of  lead,  magnesia, 
silica,  form  a list  of  ordinary  mixing  ingredients. 
These  lower  the  cost  of  the  finished  material  and  are 
often  serious  adulterants.  For  some  cases  the  addi- 
tion if  not  carried  too  far  is  not  injurious,  or  even 


44 


RUBBER  HAND  STAMP  MAKING 


may  be  beneficial.  A proper  admixture  renders  the 
gum  more  easily  moulded  and  treated  in  the  shap- 
ing processes. 


The  next  step  in  the  vulcanizing  process  is  the 
heating  of  the  mass,  which  step  is  called  curing.''^ 
Up  to  a temperature  in  the  neighborhood  of  that  of 
boiling  water  the  mixed  rubber  can  be  heated  with- 
out change  except  as  it  is  softened.  But  if  the  heat 
is  increased  it  begins  to  get  a little  more  elastic  and 
less  doughy,  and  eventually  becomes  cured  or 
vulcanized.  The  temperature  for  vulcanization  is 
about  284°  F.  (140°  0.).  The  word  about  is  used 
advisedly,  for  it  is  not  only  a question  of  heat  but  of 
time  of  exposure.  After  vulcanizing,  including  the 
curing,  india  rubber  cannot  be  moulded  to  any 
great  extent.  In  the  manufacturing  process,  there- 
fore, it  is  before  curing  placed  in  the  moulds. 


AND  THE  MANIPULATION  OF  RUBBER.  45 


heated,  shaped  by  pressure,  and  by  exposure  to  a 
higher  heat  in  a steam  oven  called  a vulcanizer,  is 
at  once  cured. 

To  prevent  adherence  to  the  moulds  they  are 
dusted  over  with  ground  soapstone,  and  the  rubber 
itself  is  often  thus  coated. 

The  methods  of  vulcanization  and  curing, , which 
may  be  of  special  use  to  the  reader,  are  given  in  the 
chapters  devoted  to  that  subject  (chapter  XL),  and 
in  the  one  devoted  to  rubber  stamps. 

Hard  rubber,  termed  ebonite  when  black,  and  vul- 
canite when  of  other  colors,  is  simply  vulcanized 
rubber  containing  a large  percentage  of  sulphur 
added  in  the  mixing  process. 

The  manufacture  of  coated  tissues  is  effected  in 
several  ways.  The  following  is  a typical  process. 
A mixture  of  one  part  washed  and  sheeted  india 
rubber  with  one  part  zinc  white,  one  fourth  part 
sulphur,  and  about  07ie.  third  part  naptha  is  mixed 
into  a dough-like  mass  and  is  spread  upon  the  cloth 
by  machinery.  The  latter  is  simple.  It  consists  of 
a bare  board  arranged  to  move  under  a scraping  bar. 
The  cloth  is  placed  on  the  board  and  carried  under 
the  bar.  The  coating  mixture  is  fed  on  one  side  of 
the  bar  upon  the  surface  of  the  cloth.  As  it  passes 
under,  a regulated  amount,  according  to  the  set  of 
the  bar,  adheres.  It  is  then  dried  by  steam  heat 
and  recoated,  until  ordinarily  six  coats,  each  about 
one  one-hundreth  of  an  inch  in  thickness,  have  been 
given.  Three  coats  are  given  in  each  direction  with 


46 


RUBBER  HAND  STAMP  MAKING. 


intermediate  drying.  The  fabric  is  then  cured  by 
heat  in  mlcanizers. 

Sometimes  the  sulphur  is  omitted  from  the  mix- 
ture and  cold  curing,  as  described  later,  is  adopted. 
When  the  goods  are  made  up  the  seams  are  secured 
with  rubber  cement,  a thick  solution  of  masticated 
gum.  Such  seams  have  to  be  vulcanized.  *” 

Sometimes  two  such  fabrics  before  curing  or  vul- 
canization, are  placed  face  to  face  and  allowed  to 
adhere  and  are  then  cured  or  vulcanized. 

Enough  has  been  said  in  this  outline  of  the  man- 
ufacturer’s treatment  of  india  rubber  to  show  that 
the  first  treatment  requires  machinery.  Very  little 
can  be  done  with  mortar  and  pestle,  although  in 
making  up  solution  these  simple  instrumentalities 
are  available.  As  a starting  point  for  making  small 
articles  masticated  sheet  rubber  and  mixed  sheet 
rubber  are  the  staple  materials.  The  preceding 
steps  are  best  accomplished  in  the  factory. 


CHAPTER  V. 


INDIA  KUBBER  STAMP  MAKING. 

We  have  seen  that  india  rubber  cannot  be  cast  in 
moulds.  Except  in  special  cases  deposition  from 
solution  is  not  available.  It  has  to  be  shaped  by  a 
combination  of  heat  and  pressure.  When  gently 
heated  it  softens  and  can  be  pressed  in  a mould. 
As  it  cools  it  retains  the  shape  thus  given  and  is 
moulded.  This  applies  to  all  unvulcanized  india 
rubber.  If  mixed  rubber  is  moulded  and  heated  to 
a higher  temperature  without  removal  from  the 
mould  the  curing  process  is  brought  about  and  the 
rubber  may  be  not  only  moulded  but  cured  and  the 
product  is  moulded  vulcanized  india  rubber.  The 
mixed  sheet  whose  manufacture  is  described  in 
chapter  IV.  (page  42)  is  the  starting  point  in  rub- 
ber stamp  making.  It  is  made  for  this  purpose  by 
the  manufacturers. 

When  the  material  is  examined  it  looks  like  ordi- 
nary white  india  rubber^  being  firm  in  texture  and 
quite  strong.  On  heating  to  280°  F.  to  290°  F. 
(137°  C.  to  143°  0.)  it  begins  to  become  cured/'’ 
and  if  in  a thin  sheet  one  to  ten  minutes  are  suffi- 
cient for  the  process.  As  the  heat  is  applied  the  in- 


48 


RUBBER  HAND  STAMP  MAKING 


dia  rubber  first  softens  and  becomes  much  like  putty. 
It  can  now  be  pressed  through  the  smallest  orifice 
and  will  fill  up  the  finest  details  of  anything  it  is 
pressed  against.  It  is  at  this  point  that  pressure 
must  be  applied  to  drive  it  into  the  interstices  of 
the  mould. 

As  the  heat  continues  it  begins  to  lose  its  doughy 
or  putty-like  consistency.  This  marks  the 'reaction 
of  the  vulcanizing  materials.  They  gradually  com- 
bine with  and  change  the  nature  of  the  caoutchouc. 
The  rubber  while  still  quite  soft  is  elastic.  If 
pressed  by  the  point  of  a knife  it  yields,  but  springs 
back  to  its  shape  when  released  from  pressure.  The 
India  rubber  is  vulcanized. 

On  removal  from  the  mould  it  will  be  found  to 
reproduce  its  smallest  detail.  The  color  and  ap- 
pearance have  not  changed  much^  but  its  nature 
and  properties  are  now  those  of  vulcanized  rubber. 
It  is  unaffected  by  heat  or  cold  within  ordinary 
ranges  of  temperature,  and  if  the  india  rubber  is  of 
good  quality  and  made  by  a proper  formula  it  will 
last  for  years. 

The  first  thing  to  be  described  is  the  mould, 
which  includes  the  arrangements  for  pressing  the 
sheet  of  india  rubber  while  heated.  A small  press 
is  needed  for  this  purpose.  It  may  be  of  the  sim- 
plest description,  and  as  an  example  of  a home- 
made but  perfectly  efficient  one  the  illustration 
may  be  referred  to.  The  base  of  the  press  is  a piece 
of  iron,  if  heat  is  to  be  directly  employed.  Where  a 


AXI)  THE  MANIPULATION  OF  RUBBER.  49 


chamber  vulcanizer  is  used  both  base  and  platen 
may  be  of  wood.  But  from  every  point  of  view  iron 
is  the  best.  It  lasts  forever,  admits  of  direct  heat- 
ing, and  does  not  split,  warp,  or  char.  Through 
two  holes  drilled  near  its  opposite  sides  two  or- 
dinary bolts  are  thrust.  It  is  best  to  use  flat 
headed  bolts,  and  to  countersink  a recess  for  the 


Simple  Vulcanizing  Press  for  Rubber  Stamps. 

heads  in  order  to  keep  the  bottom  level.  The  heads, 
may  need  to  be  filed  off  so  as  to  reduce  their  thick- 
ness, in  order  to  secure  this  object.  The  bolts  may 
be  soldered  in  place.  One  thing  should  be  care- 


50 


RUBBER  HAND  STAMP  MAKING 


fully  watched  for — the  holts  should  be  set  true  so  as 
to  rise  vertically  from  the  plane  of  the  base. 

The  platen  is  best  made  of  iron,  cut  of  the  shape 
shown.  This  is  an  excellent  disposition  of  the 
screw-bolt  slots,  as  by  swinging  the  right  end  of  the 
platen  back  it  can  be  taken  oft  without  removing 
the  nuts  and  lifting  it  over  the  ends  of  the  screws. 
Besides  the  two  nuts  fitting  the  thread  of  the  screws 
it  is  well  to  have  half  a dozen  extra  ones  larger  than 
the  others,  which  will  slip  easily  over  the  bolts,  so  as 
to  act  as  washers.  The  object  of  these  is  to  adapt 
the  press  to  objects  of  different  thickness.  The 
thread  upon  an  ordinary  bolt  does  not  extend  clear 
to  the  head,  but  by  slipping  on  some  loose  nuts  the 
plates  can  be  forced  together  if  desired. 

This  press  can  be  simplified.  Both  base  and 
platen  can  be  made  of  wood,  the  platen  being  sim- 
ply bored  for  the  bolts,  and  the  latter  driven  tightly 
through  the  holes  in  the  base  so  as  to  retain  their 
place.  Even  this  can  be  improved  on  as  regards 
simplicity.  Two  blocks  of  wood  screwed  together 
by  two  or  more  long  Avood  screArs  may  be  made  to  do 
efficient  Avork. 

One  trouble  is  apparent  Avith  all  these  devices, 
and  that  is  the  Avant  of  parallelism  of  the  opposed 
planes.  The  base  and  platen  may  be  true  and 
parallel  or  they  may  not.  Perhaps  the  simplest 
way  of  securing  this  is  the  best.  It  consists  in 
placing  across  the  base  two  distance  pieces,  which 
may  be  slips  of  wood.  These  must  have  perfectly 


A yn  THE  MA XI PULA TION  OF  R UBBER . 5 1 


parallel  faces.  As  the  press  is  screwed  up  they  will 
be  gripped  between  the  platen  and  base  and  will 
not  only  ensure  their  parallelism  but  will  keey>  them 
at  an  exact  distance  apart.  Such  distance  pieces 
are  shown  in  the  same  cut.  Pieces  of  printers^ 

furniture/^  spaces^  or  ‘^^q.uads/'’  may  be  used  for 
this  pniq^ose.  They  should  not  be  fastened  in  place 
if  there  is  need  to  adapt  the  press  to  more  than  one 
thickness  of  material  and  matrix. 

The  above  described  apparatus  is  a vulcanizing 
press.  A further  improvement  in  it  may  be  effected 
by  the  use  of  spring  pressure.  Two  strong  s|)iral 
springs  may  be  dropped  over  the  bolts,  the  nuts 
being  screwed  on  above  them,  or  a powerful  spring 
of  flat  brass  or  steel  ribband  bent  into  the  shape  of 
a shallow  letter  V may  intervene  between  nuts  and 
platen,  the  centre  of  the  bend  bearing  against  the 
centre  of  the  platen. 

As  regards  the  strength  of  the  springs  there  is 
this  to  be  said.  The  distance  pieces  will  prevent  a 
spring-  that  would  ordinarily  be  too  powerful  from 
doing  any  harm.  Such  distance  pieces  should  be 
used,  as  the  springs  must  be  based  upon  giving  a 
pressure  of  many  pounds  per  square  inch  of  surface 
to  be  acted  on.  They  should  have  a range  of  an 
eighth  of  an  inch  or  more.  The  greater  the  range 
the  more  evenly  will  they  work. 

The  next  cut  shows  an  excellent  little  screw  press, 
that  is  made  for  the  purpose  of  pressing  vulcanizing 
flasks.  This  is  so  simple  that  it  will  suggest  to  the 


52 


RUBBER  HAND  STAMP  MAKING 


mechanical  reader  how  lie  can  make  a single-screw 
press,  which  is  by  far  the  most  convenient  to  use. 
In  the  stationery  stores  very  small  model  cast  iron 
copying  presses  designed  for  use  as  paper  weights 
are  sold.  They  are  excellent  for  a limited  amount 
of  small  sized  work. 


Vulcanizing  Flask  Clamp. 


A large  sized  gas  heated  press,  such  as  made  for 
the  purpose  of  manufacturing  rubber  stamps,  is 
shown  in  the  next  cut,  p.  53.  Its  construction  is 
obvious.  It  is  termed  by  the  trade  a vulcanizer.  Its 
manipulation  will  be  given  further  on. 

Type  are  generally  the  object  to  be  copied. 
These  are  best  set  up  with  high  quads  and  spaces. 
Naturally  rather  a large  type  is  chosen,  with  extra 
wide  spaces  between  the  letters.  Some  advise  rub- 
bing the  type  faces  full  of  hard  soap,  afterwards 
brushing  ofl:  the  face,  leaving  the  hollows  filled. 
Sometimes  wax  is  recommended  for  the  same  pur- 


AND  THE  MANIPULATION  OF  PUBBER.  53 


pose.  This  prevents  the  plaster  of  the  matrix  en- 
tering so  deeply  into  the  cavities  of  the  letters. 

The  type  forming  the  model  to  be  reproduced,  is 
locked  in  a frame.  Two  pieces  of  printers^  furni- 


ture or  other  wooden  strips  screwed  together  by 
wood  screws  at  their  ends  will  answer  for  a locking- 
frame  for  small  inscriptions. 

The  model  to  be  copied  need  not  be  type,  but  any 
desired  relief  may  be  used,  such  as  an  electrotype,  a 
stereotype,  an  engraving  or  another  rubber  stamp. 
In  any  case  it  is  to  be  placed  upon  a flat  surface, 
best  an  imposing  stone  or  piece  of  marble,  with 


54 


nVBBEB  HAND  STAMP  MAKING 


the  inscription  upwards.  On  each  side  of  it  dis- 
tance pieces  reaching  about  one-eighth  inch  above 
its  upper  surface  are  to  be  placed. 

The  next  shaping  appliance  is  the  matrix  or 
mould,  or  reverse  of  the  model  which  is  to  be 
copied.  This  in  the  case  of  rubber  stamps  is  prop- 
erly called  the  matrix.  Those  who  have  witnessed 
the  stereotyping  of  a large  daily  newspaper  .have 
seen  the  matrices  of  the  type  made  of  paper  and 
paste,  the  whole  mixture  being  termed  ^^flong.'’^ 
Such  a matrix  is  required  for  rubber  type,  but 
paper  is  rather  too  susceptible  to  heat  although  good 
work  can  be  done  with  it.  It  also  does  not  enter  as 
deeply  into  the  cavities  of  the  type  as  is  desirable. 
As  a rule  a tine  quality  of  plaster  of  paris  is  to  be 
recommended.  What  is  sold  as  dental  plaster  is 
the  best,  but  common  plaster  can  be  used.  It  is 
mixed  with  water  or  with  a solution  of  gum  arabic 
or  dextrine  in  water.  For  the  latter  enough  gum 
should  be  added  to  make  the  mixing  solution  as 
thick  as  thin  syrup. 

A piece  of  iron,  perfectly  flat  and  true,  is  now  to 
be  taken,  large  enough  to  more  than  cover  the 
inscription  to  be  copied.  Upon  its  surface  a putty 
made  of  the  plaster  and  the  liquid  used  in  mixing 
is  to  be  spread.  This  should  be  rather  stiff.  The 
surface  of  the  iron  should  not  be  too  smooth  as  it  is 
desirable  that  the  plaster  should  adhere  well  on 
setting.  The  plaster  should  be  smoothly  spread  to 
a depth  of  three-sixteenths  or  a quarter  of  an  inch. 


AND  THE  MANIPULATION  OF  LUBBER.  55 

It  is  best  applied  with  a palette  knife  or  trowel, 
although  a table  knife  will  answer  perfectly.  If  its 
surface  does  not  become  smooth  it  can  be  made  so 
by  applying  a little  of  the  solution  with  the  knife 
or  trowel. 

Before  this  has  been  done  the  model  must  be 
oiled.  Olive  oil  or  other  clear  oil  is  applied  to  all 
parts  of  the  type  faces,  and  the  excess  is  then  wiped 
off  and  cleared  out  of  the  interstices  with  a piece  of 
blotting  paper. 

IS’ext  the  plate  with  the  plaster  is  inverted  and  is 
pressed  steadily  down  u]3on  the  model  until  it 
strikes  the  distance  pieces.  It  is  left  to  set.  In 
about  ten  minutes  it  can  be  raised,  wdien  it  will  be 
found  to  give  a beautiful  impression  true  to  the 
smallest  detail  of  each  letter. 

It  has  been  said  that  water  may  be  used  as  the 
mixing  fluid.  If  this  is  done  it  is  well  to  strengthen 
the  mould  by  saturating  it  with  an  alcoholic  solu- 
tion of  shellac,  after  it  has  dried  thoroughly,  best 
for  a few  hours  in  an  oven.  This  operates  to 
strengthen  the  small  projections  that  are  liable  to 
crumble  or  to  break  off  in  use. 

The  dealers  in  rubber  stamp  supplies  sell  a lever 
press  for  conducting  the  operation  of  producing  the 
matrix.  The  type  is  locked  in  a special  chase, 
which  is  carried  on  a bed  that  travels  under  and  out 
from  under  the  platen  of  the  |)ress  upon  rollers. 
From  each  corner  of  the  chase  in  which  the  type 
model  is  locked,  a pin  rises  which  is  encircled  by  a 


5() 


RUBBER  HAND  tiTAMP  MAKING 


spiral  spring.  A square  frame  of  flat  iron  with 
holes  at  the  corners  for  the  pins  to  pass  through, 
rests  upon  these  springs  well  above  the  type. 
The  pins  pass  through  holes  in  its  corners.  The 
matrix  plate  with  its  coating  of  plaster  is  placed 
upon  this  frame,  which  supports  it  above  and  not 
touching  the  type.  The  whole  is  now  rolled  under 
the  press  and  the  lever  pulled  to  produce  the  im- 
pression. As  the  pressure  is  released  the  frame 
with  the  matrix  is  raised  from  the  type  by  the 
action  of  the  springs.  This  can  be  done  immedi- 
ately, and  before  the  plaster  has  set.  It  is  almost 
impossible  to  raise  it  by  hand  with  the  requisite 
steadiness.  The  same  chase  with  corner  pins  and 
springs  can  be  used  in  a screw  press,  the  one  press 
answering  for  making  the  matrix  and  for  moulding 
and  curing  the  stamps.  The  plaster  matrix  can 
also  be  made  by  casting  from  a thinner  mixture  of 
plaster  and  w^ater.  After  the  type  has  been  set  np, 
or  the  model  has  been  selected  and  placed  face  up 
and  horizontal,  a little  ridge  or  projection  must  be 
made  all  around  it.  Paper  can  be  pasted  around  it, 
and  wound  with  thread  for  this  purpose.  It  is 
oiled  and  wiped  off  as  before.  The  plaster  is  now 
mixed  with  water  to  the  consistency  of  cream,  and 
is  poured  upon  the  model  until  it  lies  even  with  the 
projecting  ledges  or  paper  border.  In  an  hour  or 
less  it  can  be  removed.  If  water  is  used  the  mould 
should  before  use  be  treated  with  shellac  solution  as 
already  described.  The  plaster  may  also  be  mixed 


AND  THE  MANIPULATION  OF  RUBBER.  57 


with  gum  arabic  solution,  or  with  three  to  ten  per 
cent,  of  powdered  marshmallow  root.  This  in- 
creases its  toughness. 

What  is  known  as  the  oxychloride  of  zinc  cement 
appears  to  the  author  to  be  far  preferable  to  com- 
mon plaster  of  paris.  It  is  a trifle  more  expensive, 
but  it  costs  so  little  that  it  is  well  worth  trying.  It 
is  made  by  mixing  oxide  of  zinc  with  a solution  of 
zinc  chloride.  No  particular  strength  of  solution 
or  proportions  are  prescribed;  the  zinc  chloride  solu- 
tion should  be  a strong  one,  and  the  mixture  should 
be  of  about  the  consistency  of  soft  putty. 

Zinc  chloride  may  be  bought  as  a solid  substance 
or  in  strong  solution.  The  latter  answers  for  the 
mixing  directly.  It  may  also  be  simply  made  by 
dissolving  metallic  zinc  in  strong  hydrochloric  acid. 
The  manipulation  is  exactly  the  same  as  with 
plaster  of  paris. 

The  manufacture  of  papier  mache  and  of  other 
matrices  is  given  in  a special  chapter.  For  all  ordi- 
nary purposes  the  plaster  or  cement  matrices  are 
ample. 

The  stamp  is  made  from  the  mixed  uncured  sheet 
rubber,  wliose  preparation  in  the  factory,  including 
the  operation  of  calendering  it  into  sheets,  has 
already  been  described.  The  best  advice  the  reader 
can  be  given  is  not  to  attempt  to  make  it  except  as 
a matter  of  interest  and  experiment.  It  can  be 
purchased  especially  prepared  for  stamps  from  the 
dealers  in  india  rubber. 


58 


RUBBER  HAND  STAMP  MAKING 


A piece  is  cut  from  the  sheet  large  enough  to 
cover  the  face  of  the  matrix.  It  should  have  a 
perfectly  smooth  surface,  without  cloth  wrapper 
marks  sometimes  found  impressed  on  it.  The  sheet 
as  received  from  the  maker  is  about  one-eighth  of  an 
inch  thick.  It  is  Thrown  into  a box  of  powdered 
soapstone  or  talc  to  secure  a coating  of  the  same  on 
both  sides.  A little  is  dusted  over  the  matrix  and 
the  excess  is  blown  off.  The  matrix  is  now  placed 
upon  the  base  of  the  press,  and  heat  is  applied. 

To  carry  out  the  process  most  simply  the  press  if 
of  metal  may  be  placed  upon  a support  over  a gas 
burner  or  kerosene  lamp,  or  even  on  a kitchen  range 
or  stove.  It  will  in  a few  minutes  become  warm. 
The  sheet  of  india  rubber  is  now  dusted  off  and  is 
placed  in  the  press  upon  the  matrix.  The  platen  of 
the  press  is  screwed  down  upon  it. 

As  the  india  rubber  becomes  hot  it  begins  to 
soften  and  flow.  By  the  action  of  the  screw  of  the 
press  it  must  be  forced  down  from  time  to  time  as 
it  softens.  This  drives  the  putty-like  material  into 
all  the  interstices  of  the  mould.  The  excess  escapes 
from  the  sides  of  the  tympan  in  cases  where  the 
latter  is  of  restricted  area.  The  press  theoretically 
should  be  heated  to  the  vulcanizing  temperature, 
which  is  284°  F.  (140^  0.).  In  practice  the  heat  is 
not  determined  with  a thermometer.  The  operator 
learns  by  experience  how  much  heat  to  apply.  The 
regulation  type  of  gas  heated  press  or  stamp  vulcan- 
izer  is  shown  in  the  illustration  on  page  53. 


AND  THE  MANIPULATION  OF  RUB  BEE.  ^9 


As  some  of  the  India  rubber  is  sure  to  protrude, 
the  progress  of  the  work  can  be  watched  from  its 
action.  By  pressing  the  point  of  a knife  against  it 
the  period  of  vulcanization  can  be  told.  Before 
the  material  is  heated  it  is  elastic  and  resists  the 


Oil  Stove  for  Heatirg  Vulcarizers. 


pressure  of  the  knife;  as  heat  is  applied  it  becomes 
soft  like  putty;  as  the  heat  increases  it  again  stiffens 
and  becomes  quite  elastic.  At  this  point  the  press 
can  be  opened  and  the  slieet  and  matrix  can  be 
taken  out  or  the  platen  swung  aside.  On  pulling 
or  stripping  the  sheet  from  the  matrix  it  will  be 
found  to  reproduce  the  model  in  elastic  india  rubber 
to  the  minutest  detail. 

As  regards  the  minor  details  there  is  something 


60 


RUBBER  HAND  STAMP  MAKING 


to  be  said.  Distance  pieces  to  gauge  the  thickness 
have  been  recommended  for  the  home-made  press, 
page  48.  Care  must  be  taken  to  have  these  low 
enough  to  provide  for  enough  excess  of  material  to 
produce  a good  impression.  For  ordinary  stamp 
work  they  should  allow  about  one-sixteenth  of  an 
inch  for  the  squeeze.”  It  will  be  seen  that  by  using 
the  distance  or  gauge  pieces  both  for  making  the 
matrix  and  for  moulding  and  curing  the  stamp,  abso- 
lute parallelism  of  surfaces  will  be  secured. 

The  reader  will  have  noticed  in  the  description 
and  will  find  at  once  in  practice  that  the  press  has 
to  be  screwed  up  as  the  rubber  softens.  Where 
heavy  iron  presses  are  used  the  large  mass  of  heated 
iron  comprised  in  the  platen  of  the  press  instantly 
heats  the  upper  surface  of  the  India  rubber  sheet  and 
the  heat  immediately  penetrates  into  it,  while  the 
heated  matrix  heats  it  from  below.  Thus  it  softens 
at  once,  and  the  press  is  directly  turned  down  and 
the  India  rubber  is  driven  into  the  mould  and  curing 
at  once  begins.  But  where  small  presses  are  used 
this  manipulation  is  not  so  easy.  For  such  the 
springs  mentioned  on  page  51,  are  highly  to  be 
recommended.  The  matrix  and  india  rubber  can 
be  put  into  the  cold  press,  and  the  tympan  with 
intervening  springs  can  be  screwed  down  so  as  to 
compress  them.  Then  on  .applying  heat  the  mould- 
ing takes  place  automatically. 

With  a hot  press  and  good  sheet  a period  of  three 
to  ten  minutes  is  ample  for  moulding  and  curing. 


AXD  THE  MAXIPULATIOX  OF  BUB  BEE.  61 


Instead  of  sprinkling  with  talc  the  matrix  may  be 
oiled  and  sprinkled  with  plumbago  and  afterwards 
polished  with  a brush.  This  is  not  so  clean  a ma- 
terial as  talc  and  is  not  to  be  recommended  for 
general  use,  especially  as  oil  is  a bad  substance  to 
bring  in  contact  with  rubber. 

The  distance  or  gauge  pieces  whose  use  has  been 
recommended  are  not  necessary  where  jn’esses  work- 
ing truly  parallel  as  regards  their  ojDposing  faces  are 
used.  But  where  home-made  apparatus  is  used 
they  will  be  found  a valuable  addition. 

In  describing  the  simple  press  it  was  said  that  it 
could  be  made  of  wood.  It  is  evident  that  a wooden 
press  could  not  be  used  for  direct  heating.  Such  a 
press  must  be  used  in  a hot  chamber  or  vulcanizer, 
properly  so  called.  Originally  rubber  stamps  were 
generally  made  in  chamber  vulcanizers. 

The  ]iext  cut  shows  a combined  matrix  making, 
moulding  and  vulcanizing  apparatus  of  very  conven- 
ient and  compact  form  and  adapted  for  rapid  work. 
As  the  press  stands  in  the  cut  the  matrix  press  is 
seen  in  front.  A box  or  chase  is  carried  under  its 
platen  by  two  trunnions,  so  as  to  be  free  to  oscillate 
to  a limited  extent.  The  type  model  is  secured  in 
this  box.  Above  this  box  or  chase  is  a cross-bar 
with  screw  and  platen  attached,  connected  at  will  to 
two  standards  or  pillars,  so  as  to  constitute  the 
matrix  press. 

A matrix  plate  swings  on  a hinge  joint  between 
the  two  presses.  The  hinge-pin  is  removable.  Its 


62 


RUBBER  HAND  STAMP  MAKING 


ends  can  be  seen  projecting  to  right  and  left  of  the 
press  columns.  The  hinge  is  at  such  a height  that 
when  the  matrix  plate  is  swung  forward  over  the 
type  box  it  will  rest  upon  it  in  a nearly  horizontal 
position.  The  pivoted  box  will  adjust  itself  so  as 
to  come  into  parallelism  with  the  plate. 


Matrix  Making,  Moulding  and  Vulcanizing  Apparatus. 

When  the  matrix  plate  is  swung  back  it  falls 
upon  the  base  plate  of  the  vulcanizing  press  seen  in 
the  rear. 

In  use  the  composition  used  for  the  matrix  is 
spread  upon  the  matrix  plate^  which  may  for  this 


ANB  THE  MANIPULATION  OF  RUBBER.  63 


purpose  be  removed  from  the  apparatus.  It  is 
replaced  and  the  hinge-pin  is  pushed  home.  This 
is  done  with  the  composition  coated  side  facing  the 
front  of  the  apparatus  as  it  stands  in  the  cut.  The 
plate  is  then  swung  forwards,  the  platen  of  the 
matrix  press  being  turned  forward  out  of  the  way,  and 
is  pressed  down  upon  the  type  or  other  model  that 
rests  in  the  type  box.  If  desired  the  press  is  used 
to  force  it  home.  The  cross-bars  of  both  the  presses 
are  arranged  to  swing  each  one  on  one  of  the 
pillars,  so  that  the  platens  are  turned  to  one  side  out 
of  the  way  of  the  matrix  plate  as  it  is  swung  back 
and  forth. 

The  pressure  is  released  and  the  platens  are 
turned  aside.  The  matrix  plate  is  swung  over  to 
the  rear  upon  the  bed-plate  of  the  vulcanizing 
press.  Here  it  lies  with  the  composition-matrix 
upwards. 

A lighted  lamp,  either  alcohol  or  gas,  is  placed 
beneath  the  bed-plate  of  the  vulcanizing  press  on 
which  the  matrix  rests.  This  quickly  dries  it  and 
brings  it  to  a good  curing  temperature.  The  cross- 
bar and  platen  may  be  swung  over  it  during  the 
heating  so  as  to  be  heated  at  the  same  time.  The 
matrix  is  talced  when  dry  and  hot;  the  mixed  sheet 
itself  talced,  is  placed  upon  the  matrix,  the  platen 
is  screwed  down  upon  it,  and  in  a minute  or  two 
the  moulding  and  curing  is  completed. 

A vulcanizer,  properly  speaking,  is  a vessel  ar- 
ranged to  heat  to  a definite  degree  any  desired  arti- 


64 


RUBBER  HAND  STAMP  MAKING 


Rubber  Stamp  Vulcanizer. 

cles  which  are  to  be  cured.  The  favorite  type  have 
been  the  steam  vulcanizers.  If  steam  is  generated 
from  water  at  a constant  pressure,  other  things 


AND  THE  MANIPULATION  OF  RUBBER.  65 


being  equal  a constant  temperature  will  be  pro- 
duced. By  raising  or  lowering  the  pressure  the 
temperature  can  be  made  to  rise  or  fall.  A steam 
vulcanizer  is  a tightly  sealed  vessel  which  contains 
water  and  which  is  provided  with  a thermometer  or 
a pressure  gauge  as  w^ell  as  a safety-valve,  safety 
disc  or  safety  plug.  By  keeping  the  gauge  at  con- 
stant pressure  or  by  keeping  the  thermometer  con- 
stant the  temperature  can  be  limited  and  kept 
steady.  The  following  table  gives  some  pressure  in 
pounds  per  square  inch  with  temperatures  corre- 
sponding to  steam  of  such  pressures: 


Lbs.  per  square  inch. 

Temp.  Fahr. 

Temp.  Cent. 

45.512 

275° 

135° 

52.548 

284° 

140° 

60.442 

293° 

145° 

67.408 

300.2° 

149° 

The  illustration,  p.  64,  shows  a vulcanizer  of  modern 
type  made  for  rubber  stamp  work.  In  some  recent 
vulcanizers  the  water  and  steam  are  excluded  from 
the  vulcanizing  chamber,  being  contained  within 
double  w^alls  forming  a steam  jacket  and  maintain- 
ing a constant  heat  witliin  the  chamber.  These 
illustrate  a point  that  has  been  much  misappre- 
hended, namely  that  curing  is  independent  of  pres- 
sure or  atmosphere.  Because  vulcanizers  have 
generally  been  filled  with  steam  at  high  pressure 
many  have  supposed  that  the  steam  or  pressure  had 
something  to  do  with  their  action.  The  fact  is  that 


66 


RUBBER  HAND  STAMP  MAKING 


it  is  only  the  heat  due  to  the  steam  at  such  pressure 
that  is  instrumental.  Steam  is  a very  powerful 
radiator  and  absorber  of  so  called  radiant  heat.  For 
this  reason  an  atmosphere  of  steam  maintains  all 


Steam  Jacket  Vulcanizer. 

parts  of  the  vulcanizer  at  an  even  temperature  and 
is  to  that  extent  advantageous.  Its  presence  and 
the  pressure  it  generates  are  not  by  any  means  re- 
quired for  vulcanizing.  Its  pressure  is  entirely 
without  effect. 

To  use  a steam  vulcanizer^  water  is  introduced, 


AND  THE  MANIPULATION  OF  RUBBER.  67  . 


the  article  in  the  press  or  mould  is  placed  in  it,  and 
the  top  is  secured.  Heat  is  then  applied,  best  if  on 
the  small  scale,  from  a Bunsen  gas  burner  gas, or  oil 
stove.  Either  the  pressure  gauge  or  thermometer 
may  be  watched,  and  the  flame  turned  up  or  down 
to  keep  it  at  the  |)i’oper  temperature. 

Moulding  cannot  be  executed  in  the  ordinary 
closed  chambers.  The  press  must  flrst  be  heated  to 
the  temperature  of  boiling  water  or  thereabouts  and 
the  moulding  is  then  effected  by  screwing  down  the 
mould  screw,  upon  the  sheet  and  matrix.  It  is 
then  placed  in  the  vulcanizer  and  cured. 

The  manufacturers  supply  gas  regulators  which 
automatically  regulate  the  gas  supply.  These  are 
worked  by  the  steam  pressure.  If  any  one  wishes 
to  study  the  practical  manipulation  of  small  steam 
vulcanizers  he  can  see  them  in  use  at  any  dentist^s 
office. 

There  is  no  need  of  a steam  vulcanizer  for  ordi- 
nary stamp  work.  The  hot  press  system  already  de- 
scribed answers  every  purpose  and  is  in  use  by  the 
most  advanced  manufacturers  for  thin  sheet  work. 
But  if  a wooden  moulding  press  is  used  then  it  must 
be  heated  in  a vulcanizer  or  some  kind  of  oven  or 
hot  chamber. 

A very  simple  and  reasonably  satisfactory  oven  or 
air  bath  can  be  made  from  a flower  pot  and  a couple 
of  tin  plates.  A plate  larger  in  diameter  than  the 
mouth  of  the  flower  pot  forms  the  base  of  tho  ap- 
paratus. This  is  supported  on  a stand  over  the  gas 


68 


RUBBER  BAND  STAMP  MAKING 


lamp  or  other  source  of  heat.  A smokeless  flame  or 
one  depositing  no  lampblack  should  be  used.  Alco- 
hol or  a kerosene  oil  stove  illustrated  on  page  59  are 
excellent.  On  this  plate  a smaller  plate  is  inverted, 
which  latter  must  be  so  small  as  to  be  surrounded 
by  the  flower  pot  and  to  be  included  within  it  when 
the  pot  is  placed  over  it  like  an  extinguisher. 


Flower  Pot  Vulcanizer  on  Stand. 


A chemical  or  round  stemmed  thermometer  is 
arranged  to  go  through  the  aperture  in  the  up- 
turned bottom  of  the  pot.  This  may  be  hung  from 
a support  or  it  may  be  secured  by  passing  through 
a hole  in  a cork  or  block  of  wood.  Its  bulb  should 


AND  THE  MANIPULATION  OF  RUBBER.  09 


be  near  the  part  of  the  chamber  to  be  occupied  by 
the  mould  or  press. 

The  press  with  the  article  to  be  cured  is  placed 
upon  the  inner  plate.  The  temperature  is  main- 
tained at  the  proper  point  by  regulating  the  heat, 
and  all  the  conditions  for  excellent  work  are  sup- 
plied. The  disposition  of  the  apparatus  is  shown  in 
the  cuts. 


InTKKIOR  op  FLOWPH  I’OT  VULCANIZER. 

Another  arrangement  equally  simple  is  given  in 
the  next  cut.  An  iron  kettle  has  a layer  of  type 
metal  or  lead  poured  an  inch  thick  cast  within  it 
upon  its  bottom.  A thermometer  passing  through 
a hole  in  the  cover  enters  a cup  of  glycerine  that 
stands  upon  the  bottom.  This  gives  the  tempera- 
ture. 

The  object  of  having  a thick  or  a double  bottom 
is  to  prevent  excessive  radiation  of  heat  from  any 
one  part.  The  essential  condition  for  good  opera- 


70  BUBBEU  BAND  STAMP  MAKING 

tion  is  to  maintain  an  even  temperature  throughout 
the  chamber. 


The  thermometer  is  not  an  absolute  necessity. 
By  removing  the  press  from  time  to  time  and  in- 
specting the  overflow  of  india  rubber  the  progress 
of  the  operation  can  be  watched.  An  extra  piece 
of  india  rubber  may  be  placed  on  a piece  of  wood 
by  the  side  of  or  upon  the  wooden  portion  of  the 
press,  and  its  condition  can  be  taken  as  the  crite- 
rion. Pressure  with  the  point  of  a knife  will  tell 
the  vulcanizing  point. 

By  the  press  system  of  curing,  a heat  far  above 
the  vulcanizing  temperature  may  be  made  to  do 
good  work  by  a very  short  application.  There  is 


AND  THE  MANIPULATION  OF  RUBBER.  71 


however  danger  of  burning  the  ^work  if  left  in  too 
long.  If  the  air-bath  with  thermometer  or  the 
steam  vulcanizer  is  used,  and  the  heat  is  kept  down 
to  the  proper  curing  temperature,  there  is  no  danger 
of  burning  the  india  rubber  even  if  the  curing  is 
considerably  prolonged. 

As  the  flower  pot  has  often  to  be  lifted  off  for 
introduction  or  removal  of  the  press,  and  as  it  gets 
quite  hot,  a holder  of  some  kind  is  requisite.  A 
piece  of  heavy  blotting  paper  is  very  convenient  for 
this  purpose. 

The  flower  pot  system  with  thermometer  can  be 
further  simplifled  by  being  used  on  a stove  or  range. 
A china  saucer  inverted,  or  some  similar  support, 
should  be  placed  under  the  pot.  A part  of  the 
stove  at  very  low  heat  will  suffice.  The  kettle  vul- 
canizer, can  also  be  placed  on  a stove  so  as  to  dis- 
pense with  gas  or  oil. 

Finally^  as  the  last  step  in  simplifying  the  work,  a 
stamp  can  be  made  without  any  special  apparatus 
beyond  a hot  flat  iron.  The  matrix  may  be  placed 
on  a stove  where  the  heat  is  rather  low,  the  talc- 
coated  mixed  rubber  sheet  placed  upon  it,  and  on 
this  a hot  flat  iron.  In  a few  minutes  if  the  heat  is 
sufficient  the  stamp  will  be  finished. 

A few  words  may  be  said  about  the  type.  High 
spaces  and  quads  between  the  letters  should  be  used, 
such  as  will  come  up  to  the  shoulder  of  the  type,  as 
has  been  said.  But  a very  nice  effect  is  produced 
by  using  low  quads  between  words.  This  leaves 


72 


RUBBER  HAND  STAMP  MAKING. 


each  word  elevated  by  itself,  producing  a good 
appearance. 

Autograph  stamps  are  made  from  a model  cut  in 
wood  by  a wood  engraver.  The  autograph  is  writ- 
ten in  some  form  of  copying  ink  upon  a piece  of 
paper,  and  is  transferred  by  moistening  and.  pres- 
sure to  a block  of  wood.  With  an  engraver’s  tool 
the  wood  is  cut  away  from  the  lines,  as  the  block  is 
routed  after  the  inscription  has  been  ^‘'outlined.” 
The  woodcut  is  used  as  a model  for  making  a 
matrix. 

It  is  evident  that  an  autograph  of  fair  quality 
could  he  obtained  from  a chalk  plate.  But  in  rub- 
ber stamp  work  to  get  good  results  certain  essential 
parts  should  be  of  the  best.  These  parts  include 
the  mixed  rubber,  model  and  matrix.  A departure 
from  excellence  in  any  of  these  tends  to  the  produc- 
tion of  an  inferior  stamp.  What  is  known  as  a 
‘Miealthy  cure”  is  above  all  essential  to  the  appear- 
ance of  the  j)roduct. 

The  stamp  thus  made  is  attached  to  a wooden 
handle  by  common  glue  or  by  one  of  the  rubber 
cements  given  in  chapter  XVI. 


CHAPTER  YI. 


INDIA  KUBBER  TYPE  MAKING. 

India  rubber  type  are  often  used  to  set  up  differ- 
ent inscriptions  in  wooden  bandies,  or  different  date 
figures  in  rubber  stamps.  The  latter  are  in  such 
cases  made  with  slots  or  recesses  to  receive  them. 
Rubber  type  are  much  shorter  than  regular  type, 
and  as  a rule  are  larger  in  the  body  in  proportion  to 
the  face  of  the  letter.  Where  only  a few  are  re- 
cpiired  the  following  process  is  the  simplest  way  of 
making  them  from  mixed  rubber  slieet. 

Tlie  type  which  are  to  be  copied  are  set  up  on  a 
level  base  or  imposing  stone,  and  quads  or  spaces 
are  put  between  them.  High  quads  and  spaces 
should  be  used;  otherwise  they  should  be  pushed  up 
until  even  with  the  shoulders  of  the  type.  After 
oiling  the  faces  a matrix  is  produced  exactly  as 
described  for  stamps.  Before  it  has  set  quite  hard 
the  plaster  or  cement  is  cut  off  so  that  it  will  just  fit 
within  a little  flask  or  frame. 

The  latter  may  be  made  of  tin  or  wood  and  may 
be  rectangular  or  circular,  provided  it  is  large 
enough  to  include  within  its  area  the  full  working 
face  of  the  matrix.  It  should  be  about  half  an  inch 


74 


RUBBER  HAND  STAMP  MAKING 


or  five-eighths  of  an  inch  deep.  Its  object  is  to  pre- 
vent the  softened  india  rubber  from  spreading,  so 
as  to  secure  the  requisite  height  of  the  type  pro- 
duced. 

A piece  of  wood  or  metal  is  cut  so  as  to  fit  closely 
within  this  frame  like  a plunger.  It  is  provided 
with  shoulders  or  cross  pieces,  so  as  to  limit  the 
depth  to  which  it  can  be  inserted.  It  will  be  seen 
that  when  matrix,  fiask,  and  plunger  are  all  put 
together  a complete  mould  for  a block  of  type  is 


India  Rubber  Type  Mould, 


produced,  as  shown  in  the  illustration,  the  matrix 
with  its  plate  forming  the  bottom  of  the  box. 
After  the  flask  is  placed  upon  the  matrix  it  is  filled 
with  the  mixed  uncured  india  rubber  sheet.  As  a 
matter  of  preference  thick  sheet  is  used,  but  scraps 
of  all  shapes  can  be  employed  as  it  all  fuses  to- 
gether. The  mould  and  matrix  are  of  course  first 
well  dusted  with  talc  powder.  The  plunger  is  put 
on  and  the  whole  is  pressed.  Heat  is  next  applied 
in  a vulcanizer  or  hot  air  chamber,  such  as  the 
flower  pot  arrangement,  or  in  boiling  water.  As  the 
sheet  reaches  the  boiling  point  212°  F.  (100°  0.)  the 
flask  is  removed  and  the  plunger  examined.  If  it 


AND  THE  MANIPULATION  OF  RUBBER.  75 

goes  down  to  its  seat  without  expelling  any  india 
rubber  more  of  the  latter  is  required  and  is  accord- 
ingly inserted,  the  plunger  being  taken  otf  for  the 
purpose.  The  softened  gum  should  ooze  out  around 
the  sides  of  the  plunger.  The  whole  is  again  put 
under  pressure,  and  the  platen  is  screwed  down,  and 
if  all  is  right  an  excess  of  rubber  showing  itself,  the 
whole  is  put  in  the  hot  chamber,  the  heat  is  raised 
to  284°  F.  (140°  C.),  and  is  maintained  there  for 
half  an  hour. 

It  is  almost  a necessity  to  secure  the  matrix  plate 
to  the  bottom  of  the  flask.  This  for  a single  opera- 
tion may  be  done  by  screws,  or  for  several  operations 
by  hooks  or  catches. 

When  the  curing  is  complete  the  mould  is  re- 
moved from  the  vulcanizer,  is  allowed  to  cool  and  is 
opened.  The  block  of  type  will  come  out  with  per- 
fect reproduction  of  the  letters  upon  one  side.  If 
all  the  directions  have  been  followed  as  regards  dis- 
tance pieces,  level  imposing  surface,  etc.,  both  faces 
will  be  exactly  parallel,  and  any  number  of  other 
blocks  can  be  reproduced  of  exactly  the  same 
height,  not  necessarily  from  the  same  matrix, 
although  one  good  matrix  can  be  used  many  times. 

The  type  have  now  to  be  cut  apart.  This  is  done 
with  a sharp  knife  which  is  kept  wet.  It  is  worked 
with  a sawing  motion,  and  if  sharp  and  properly 
used  will  cut  with  regularity,  and  smoothly.  Type 
with  knife  marks  on  the  sides  are  always  unmechan- 
ical in  appearance  and  seem  to  be  ^Miome  made.'’^ 


76 


RUBBER  HAND  STAMP  MAKING. 


The  object  of  using  high  quads  and  spaces  or  of 
pushing  them  up,  will  now  he  evident.  It  secures 
the  evenness  of  the  general  face  of  the  block  of 
letters,  which  otherwise  would  have  a deep  depres- 
sion between  each  pair  of  letters.  If  the  quads  and 
leads  are  properly  arranged,  the  letters  will  project 
upwards  from  a smooth,  plane  surface. 

The  dealers  in  rubber  stamp  maker’s  supplies  sell 
special  steel  moulds  for  the  purpose  of  making 
them.  This  does  away  with  all  necessity  for  making 
matrices,  and  making  up  a flask,  etc.  The  general 
manipulation  is  that  given  above.  Where  many  are 
to  be  made  the  regular  mould  is  by  all  means  to  be 
recommended. 

Sometimes  type  are  made  by  cementing  single 
letters  made  by  the  stamp  process  upon  wooden 
bodies. 


CHAPTER  yiL 


THE  MAKING  OF  STAMPS  AHD  TYPE  FEOM  VULCAN- 
IZED INDIA  KUBBER. 

Although  all  reference  hitherto  in  the  matters  of 
stamps  and  type  has  been  to  their  manufacture  from 
uncured  india  rubber,  a good  deal  can  be  done  with 
vulcanized  and  cured  gum.  The  stock  that  is 
known  in  the  trade  as  ^^ure  gum,  such  as  is  used  for 
bicycle  tyres,  for  steam  packing  and  the  like,  can 
be  made  to  yield  to  moulding  to  a certain  degree. 
It  will  not  flow  and  unite  as  will  the  uncured  gum, 
but  it  is  evident  that  in  certain  cases  its  stiffness  is 
even  an  advantage.  Thus  with  it,  rubber  type  can 
be  made  without  any  flask  or  frame.  The  material 
has  stiffness  enough  to  support  itself. 

The  manipulation  is  of  the  simplest.  A piece  is 
cut  out  with  a knife  so  as  to  be  of  proper  thickness 
and  size.  It  should  be  a little  thicker  than  will 
ultimately  be  required.  The  two  opposite  surfaces 
should  be  smooth  and  parallel.  It  is  talced,  and 
placed  in  the  press  with  the  matrix  beneath  it,  and 
subjected  to  pressure  by  the  screws  being  turned 
down.  It  is  then  placed  in  the  vulcanizing 
chamber  and  heated  to  about  284°  F.  (140°  0.). 


78 


RUBBER  HAND  STAMP  MAKING 


After  it  has  become  hot  it  softens  a little.  The 
press  is  removed  from  the  hot  chamber  and  is  again 
screwed  down  as  hard  as  the  matrix  can  stand. 
This  point  is  largely  a matter  of  judgment.  The 
heat  is  largely  indifferent  as  long  as  it  is  anywhere 
near  the  above  temperature. 

By  one  or  two  repetitions  of  the  pressing  and 
heating  the  softened  india  rubber  can  be  made  to 
take  quite  a deep  impression  from  a suitable  matrix. 
It  is  allowed  to  cool  under  full  pressure.  When 
removed  from  the  press,  it  will  retain  the  characters. 

It  is  evident  that  impressions  in  as  high  relief  or 
as  deep  and  clear  as  those  yielded  by  uncured  india 
rubber  need  not  be  expected.  But  where  the  other 
cannot  be  had,  or  where  some  experimental  or  tem- 
porary work  only  is  on  hand,  this  process  will  be 
very  convenient. 

The  material  may  be  half  an  inch  thick.  From 
such  india  rubber  type  can  be  cut  with  advantage. 

Old  rubber  can  be  thus  used.  The  writer  has  ob- 
tained excellent  results  from  pieces  of  an  old  dis- 
carded bicycle  tyre. 

The  great  point  is  to  apply  a heavy  pressure  to 
the  hot  material.  Many  other  articles  can  be  thus 
produced  extemporaneously.  At  the  same  time  it 
must  be  considered  only  a makeshift.  One  who  has 
used  the  soft,  easy  flowing  uncured  gum  would 
never  be  reconciled  to  the  use  of  so  rigid  and  diffi- 
cultly moulded  a material,  one  too  that  can  never 
be  trusted  to  reproduce  intricate  moulds  of  consid- 


AND  THE  MANIPULATION  OF  RUBBER.  79 


erable  depth.  In  the  slow  yielding  of  the  half 
melted  uncnred  gum,  so  amenable  to  slight  pressure, 
a quality  of  availability  is  found  that  is  missed  in 
the  other.  One  is  worked  by  main  force  where  the 
other  readily  yields  and  takes  the  most  complicated 
shapes. 

By  the  above  process  stamps  of  such  thickness 
may  be  made  that  they  can  be  used  without  handles. 
It  is  also  useful  for  impressing  a designation  of  any 
kind  upon  ready  cured  articles.  It  suggests  a very 
useful  department  of  manipulation  of  india  rubber. 

The  heating  and  moulding  can  be  done  also  in  a 
hot  liquid  bath  such  as  described  in  chapter  XI. 


CHAPTER  VIII. 


VARIOUS  TYPE  MATRICES  FOR  RUBBER  STAMPS  AND 
TYPES. 

Matrices  for  stamp  moulds  can  be  made  by  sev- 
eral of  the  methods  used  by  stereotypers.  Thus  an 
electrotype  could  be  taken  directly  from  the  face  of 
the  type.  There  would  be  little  or  no  utility  in 
doing  this  where  the  simpler  processes  are  available. 

PAPIER  MACHE  MATRICES. 

The  stereotyper  for  daily  newspaper  work  uses 
very  generally  the  papier  mache  or  v lloiig  ” process 
of  reproducing  the  page.  This  is  also  available  for 
rubber  stamp  making. 

The  first  requirement  is  paste.  This  is  made  by 
softening  twelve  parts  of  whiting  in  forty  parts  of 
water,  letting  it  soak  for  an  hour  or  more.  Nine 
parts  of  wheat  fiour  are  added.  This  is  best  mixed 
with  a little  water  before  adding  to  the  main  mix- 
ture. It  is  then  brought  to  the  boil  and  seven  parts 
of  glue  softened  by  soaking  in  twenty-one  parts  of 
water,  are  added.  For  each  gallon  of  such  mixture, 
one  ounce  of  white  crystallized  carbolic  acid  is 
added  if  it  is  to  be  kept  for  a long  time. 


AND  THE  MANIPULATION  OF  RUBBER.  81 


The  flong  is  made  by  pasting  together,  one 
on  top  of  the  other,  a sheet  of  fine  hard  tissue 
paper,  three  sheets  of  blotting  paper  (about  23 
pounds  to  the  ream),  and  a heavy  sheet  of  manilla 
paper.  The  pasting  must  be  smooth  and  each 
layer  must  be  pressed  and  rubbed  down,  but  not  too 
hard.  It  is  very  important  to  secure  perfect 
smoothness  and  regularity,  and  entire  absence  of 
air  bubbles. 

Every  printing  office  where  the  process  is  used 
has  its  own  traditions  as  to  the  preparation  of  flong. 
As  a great  deal  depends  on  manipulation,  it  would 
be  well  to  endeavor  to  inspect  its  practical  use  in  a 
newspaper  printing  office  before  making  it.  Eeady 
prepared  flong  can  also  be  procured. 

The  form  of  type  must  be  very  clean  and  there 
must  be  no  paste  on  the  tissue  paper  face  of  the 
flong.  The  type  are  lightly  oiled,  some  powdered 
talc  is  dusted  over  the  damp  tissue  paper  face  of 
the  flong,  and  the  mass  is  laid  face  downward  on 
the  type.  With  a stiff  haired  brush  the  paper  is 
now  beaten  down  against  the  type.  Great  care 
must  be  taken  to  beat  vertically;  a slight  side  action 
will  ruin  the  resulting  matrix.  If  the  brown  paper 
will  not  stand  the  beating,  a cloth  may  be  spread 
over  it. 

The  progress  of  the  work  can  be  watched  by  rais- 
ing up  a corner  from  time  to  time.  When  suffi- 
ciently deep  the  last  touch  is  given  by  the  printer’s 
planer.  This  is  a block  of  hard  wood.  It  is  placed 


82 


RUBBER  HAND  STAMP  MAKING 


upon  the  back  of  the  flong  and  is  hammered  down. 
The  operation  is  repeated  until  the  entire  area  has 
been  treated.  For  much  rubber  stamp  work  the 
area  would  be  so  restricted  that  shifting  would  be 
unnecessary. 

The  work  is  then  put  into  a heated  screw  press, 
such  as  the  vulcanizing  and  matrix  press,  and  is 
dried  for  a period  varying  from  some  minutes  up  to 
half  an  hour.  Some  blotting  paper  is  advanta- 
geously pressed  on  top  of  the  whole  in  the  press 
while  drying.  The  press  is  opened,  the  flong  re- 
moved, and  dried  in  an  oven.  It  is  kept  under  a 
piece  of  wire  net  while  drying  to  keep  it  flat.  The 
net  may  be  of  wire,  .064  inch  thick,  with  six 
meshes  to  the  inch.  This  baking  is  not  strictly 
necessary  for  rubber  stamp  work. 

This  gives  a matrix  which  may  be  used  as  rub- 
ber stamp  moulds.  In  use  it  is  recomended  to 
place  a piece  of  smooth  tin  foil  over  it.  This  tends 
to  give  a smoother  surface  to  the  rubber. 

STRUCK  UP  MATRICES. 

DidoFs  polytype  process  may  be  advantageously 
used  for  producing  type  metal  matrices.  The  fol- 
lowing is  the  method  of  applying  it. 

The  type  form  is  firmly  locked  and  is  backed  up 
by  and  secured  to  a solid  block  of  wood.  It  is  sus- 
pended in  a sort  of  gallows  frame  with  the  face  of 
the  type  downward  and  exactly  level  a few  inches 
above  a table.  Underneath  it  a shallow  tray  is 


AND  'THE  3fANIPULATI0N  OF  EUBBEli-  8B 


placed,  inta  which  some  melted  type  metal  is 
poured.  The  melted  metal  is  carefully  watched. 
The  block  and  type  are  held  by  a catch  so  as  to  be 
released  at  will.  Just  as  the  type  metal  is  on  the 
point  of  solidifying,  the  block  is  released  and  drops 
upon  the  metal  in  the  tray.  The  type  should  be 
slightly  oiled.  The  force  of  the  blow  produces  a 
matrix  in  the  metal,  and  the  form  can  at  once  be 
removed. 

It  is  well  to  have  accurately  adjusted  distance 
pieces  for  corresponding  striking  pieces  on  the  type 
block  to  impinge  upon.  The  process  is  highly 
spoken  of,  especially  for  small  forms  such  as  those 
mostly  required  for  rubber  stamps. 

CHALK  PLATES. 

The  base  for  this  form  of  matrix  is  a metal 
plate  whose  surface  is  slightly  roughened  with  sand- 
paper. It  is  next  rubbed  over  with  white  of  egg, 
and  flooded  with  the  chalk  wash  made  as  follows: 
Flong  paste  (described  under  Papier  Mache  Ma- 
trices, page  80),  six  ounces;  whiting,  twenty-four 
ounces;  water,  three  pints.  The  whiting  is  softened 
by  soaking  for  an  hour  or  more.  The  whole  must 
be  intimately  mixed.  It  should  cover  the  plate  to 
the  depth  of  one-thirtieth  to  one-twentieth  of  an 
inch.  The  plate  is  dried  in  a perfectly  horizontal 
j)Osition. 

AVlien  dry  the  design  or  writing,  etc.,  is  made 
with  a smooth  steel  point,  the  lines  being  carried 


84 


RXJBBEB  HAND  STAMP  MAKING. 


clear  through  the  white  layer  to  the  metal.  The 
mould  is  now  baked  at  a temperature  well  above 
boiling  water;  as  high  as  392°  F.  (200°  C.)  may  be 
reached  without  harm. 

If  the  coating  seems  too  thin^  an  extra  coat  can 
be  given  between  the  lines  especially  over  the  larger 
areas.  This  must  be  done  before  the  baking.  A 
pipette  may  be  used  for  putting  on  this  coat.  This 
deepening  has  the  bad  effect  of  increasing  the 
chance  of  the  coating  stripping  from  the  metal. 

The  matrix  thus  prepared  is  used  in  the  press 
just  as  is  the  ordinary  plaster  matrix.  It  is  suited 
for  reproduction  of  autographs,  scrip,  diagrams, 
etc. 


CHAPTER  IX. 


THE  MAKING  OF  VARIOUS  SMALL  ARTICLES  OF  INDIA 
RUBBER. 

India  robber  can  be  so  readily  shaped  in  moulds 
and  the  latter  are  so  readily  made  of  plaster  of  paris 
that  any  one  who  is  interested  in  such  things  will 
find  endless  amusement  in  working  out  different 
designs.  Before  suggesting  any  specific  articles 
the  following  are  the  general  points  to  be  kept  in 
mind. 

The  material  may  be  uncured  mixed  sheet  of  any 
thickness.  As  we  have  seen  this  material  when 
heated  and  pressed  runs  together.  It  can  be  forced 
into  any  shape  by  comparatively  slight  pressure. 
So  exactly  does  it  reproduce  the  smallest  line  or 
mark,  that  care  must  be  taken  to  have  the  moulds 
very  smooth  and  free  from  defect.  Powdered  soap- 
stone is  used  to  prevent  adherence  to  the  mould,  but 
great  care  must  be  taken  not  to  mix  it  among  the 
pieces  of  the  india  rubber,  where  several  are  used 
in  one  article,  as  it  will  prevent  their  coalescing 
or  running  together. 

Another  point  is  to  contrive  to  introduce  the 
proper  quantity  of  rubber.  The  aim  must  be  to 


86 


EUBBER  HAND  STAMP  MAKING 


have  a slight  excess,  but  to  avoid  waste  this  should 
be  as  little  as  possible.  Unless  some  rubber  is 
squeezed  out  there  is  no  certainty  that  the  mould 
has  been  filled.  Any  projecting  ‘‘^fins""  from  the 
overfiow  are  cut  off  with  a knife  or  scissors  after  the 
article  is  removed  from  the  mould. 

Plaster  of  paris  or  dental  plaster  mixed  with  dex- 
trine or  gum  arabic  water  or  the  zinc  oxychloride 
cement,  already  described,  is  to  be  recommended  for 
the  moulds.  They  should  be  made,  if  deep,  in 
frames  or  fiasks  of  tin,  as  plaster  if  unsupported 
is  liable  to  split  open  when  the  rubber  is  forced  home. 

For  many  articles  the  hot  press  can  be  used. 
Such  articles  are  mats  and  other  thin  fiat  pieces. 
The  rubber  stamp  sheet  is  a good  material  for  them. 
For  thicker  articles  a thicker  sheet  can  be  used,  and 
sheet  of  any  gauge  can  be  procured  from  the  maker. 
Much  of  what  has  been  said  about  india  rubber  type 
applies  to  the  making  of  miscellaneous  shapes.  It 
will  also  be  understood  where  wooden  moulds  are 
spoken  of  that  plaster,  or,  still  better,  metal  can  be 
substituted,  and  is  to  be  recommended  for  nice 
work  as  the  grain  of  the  wood  is  very  apt  to  show 
where  the  india  rubber  comes  in  contact  with  it. 

Suction  discs  and  similar  small  articles  into  which 
an  extra  thickness  of  india  rubber  enters  are  best 
cured  in  a vulcanizer.  The  fiower  pot  arrangement 
is  excellent  for  such.  The  time  for  curing  may 
be  somewhat  extended  on  account  of  the  greater 
thickness  of  material  to  be  acted  on. 


AND  THE  MANIPULATION  OF  RUBBER.  87 


Suction  Discs. — For  suction  discs  a mould  is 
required  which  will  produce  a shallow  cup  with  the 
edge  feathered  or  reduced  to  a very  slight  thickness. 
Its  outer  surface  should  be  raised  in  the  centre  so 
as  to  give  a projection  for  attachment  of  the  hook. 
The  discs  are  generally  made  small,  not  over  an  inch 
in  diameter,  as  they  are  not  reliable  for  any  heavy 
service.  Their  principal  use  is  to  suspend  advertis- 
ing cards  and  light  articles  to  the  glass  of  show 
windows.  The  following  is  a method  of  making  a 
simple  mould. 

A hole  to  give  the  outside  contour  should  be 
bored  in  a small  piece  of  wood.  A marble  which 
will  exactly  fit  the  hole  is  next  required.  Some 
plaster  of  paris  is  mixed  with  water  and  put  into  the 
bottom  of  the  hole,  and  the  oiled  marble  is  pressed 
down  until  the  plaster  rises  and  fills  the  entire  space 
under  the  marble.  After  it  has  set  the  marble  is 
removed.  The  proportions  should  be  so  arranged 
that  the  plaster  will  have  risen  at  the  sides  within 
an  eighth  of  an  inch  of  the  surface  of  the  wood. 
This  gives  the  exterior  mould.  For  the  cup  or 
hollow  a marble  a shade  too  large  to  enter  the 
hole  may  be  used. 

One  or  if  necessary  two  thicknesses  of  mixed 
sheet  rubber  cut  into  disc  shape  so  as  to  fit  the 
hole  are  inserted  in  the  block,  and  the  larger  marble 
is  placed  on  top  and  screwed  down  by  the  press. 
Heat  is^now  applied  in  the  vulcanizer.  When  the 
thermometer  indicates  212°  F.  (100°  0.),  or  better  a 


I 88  RUBBER  HAND  STAMP  MAKING 

little  more,  the  mould  is  withdrawn  and  the  screws 
turned  until  the  rubber  is  forced  down  and  the 
excess  begins  to  squeeze  out  between  the  marble  and 
the  wood,  which  two  should  now  nearly  touch.  It  is 
replaced  and  the  heat  is  brought  up  to  the  curing 
temperature  284°  F.  (140°  C.).  It  is  possible  that 
a second  screwing  up  may  be  needed.  The  spring 
press  is  in  such  cases  particularly  convenient  as  it 
avoids  the  necessity  for  re- 
moving the  press  from  the 
vulcanizing  chamber.  After 
half  an  hour  it  will  be  thor- 
oughly cured.  A hole  is 
made  through  its  centre  from 
,;i  side  to  side  thereof,  but  not 

;!  penetrating  the  disc,  and 

I through  this  hole  a brass 

I nail  is  thrust  and  bent  into 

I ■ hook  form. 

In  the  cut  the  correct  shape  for  the  mould  and 
I ' consequently  for  a suction  disc  is  shown.  This  can 
I'  be  easily  secured  where  a disc  already  made  is  procur- 

f able  by  casting  in  plaster,  or,  with  a little  ingenuity 

the  template  for  the  mould  and  the  plunger  to  be 
i used  instead  of  the  marble  can  be  whittled  out  of 

wood.  The  lower  body  of  the  mould  in  such  a case 
can  be  made  of  plaster  of  paris.  To  secure  the 
alignment  of  the  two  parts  of  the  mould,  dowel  pins, 
indicated  in  dotted  lines,  should  be  placed  near  the 
periphery.  The  gum  should  be  introduced  in  a lump 


Mould  for  Suction  Discs. 


And  THt:  MANIPULAtlON  OF  BUBBFB.  89 


near  the  centre,  in  order  that  it  may  sink  well  down- 
wards to  the  bottom  of  the  mould  before  spreading 
laterally.  Sometimes  the  tips  have  a recessed 
end.  This  is  secured  by  the  use  of  a mandrel, 
shown  in  dotted  lines  in  the  axis  of  the  mould. 
Such  discs  are  sometimes  made  to  be  cemented  to 
arrows  to  be  discharged  against  smooth  surfaced 
targets,  to  which  they  adhere  on  impact  by  atmos- 
pheric pressure,  giving  rise  to  a very  interesting 
game. 

Another  use  of  suction  discs  is  as  photographic 
negative  holders.  They  can  be  fastened  to  a wooden 
handle  and  be  attached  by  suction  to  the  back  of 
a negative  under  treatment.  For  this  purpose  they 
should  be  at  least  two  inches  in  diameter. 

Pencil  Tijjs. — These  are  generally  little  cylinders 
of  india  rubber,  which  fit  into  a tube  that  slides 
over  the  end  of  the  pencil.  They  can  be  thus  sim- 
ply made.  A hole  is  bored  in  a piece  of  wood  the 
diameter  of  and  a little  more  than  the  depth  of 
the  pencil  tip.  A short  cylinder  that  exactly  fits 
the  hole  is  required  for  plunger.  The  gum  is  put 
into  the  hole  in  little  discs,  or  rolled  up  into  a 
cylinder,  the  jDl^^nger  is  placed  on  top,  and  the 
mould  put  in  the  press.  It  is  shaped  by  pressure 
and  cured  as  described. 

Sometimes  the  tips  are  cup  shaped.  For  these 
the  mould  is  made  in  two  sections  fastened  by 
catches  or  by  pins  set  in  the  plaster  as  shown  in  the 
cut.  The  hole  is  made  larger  at  bottom  than  at 


90 


RUBBER  HAND  STAMP  MAKING 


top,  and  at  the  top  is  a little  smaller  than  the  shaft 
of  the  pencil.  A plunger  that  nearly  fits  the  small 
end  is  provided.  The  india  rubber  is  placed  in  the 
mould  and  heated.  When  soft,  the  plunger  is 
forced  down  to  the  proper  distance  in  the  press 
and  the  article  is  cured.  Care  must  be  taken  to 


give  the  plunger  a good  coating  of  talc,  and  it  must 
be  made  to  sit  vertically.  The  arrangement  of  a 
cylindrical  hole  shown  in  the  cut  secures  this  result 
perfectly.  As  distance  piece  a pin  is  passed  through 
the  plunger. 

Cane  and  Chair  Leg  Tips,  etc, — By  carrying  out 
the  process  just  described  with  larger  moulds  and  of 
slightly  different  section  very  convenient  tips  for 
chair  legs  and  walking  canes  can  be  made.  Such 
tips  can  be  modified  in  size  and  thickness  to  answer 
as  covers  for  the  mouths  of  bottles,  test-tubes,  etc. 

Corks, — These  may  be  made  in  moulds  tapering 


AND  THE  MANIPULATION  OF  RUBBER.  91 


from  top  to  bottom.  The  india  rubber  must  be 
packed  in  with  great  care  to  secure  as  solid  filling  as 
possible.  A plunger  is  used  that  enters  the  larger 
end  and  is  a very  little  smaller  in  diameter,  so  as  to 
descend  a little  way  into  the  mould.  This  distance 
determines  the  length  of  the  cork.  As  the  perim- 
eter of  the  plunger  strikes  the  walls  of  the  mould 
it  cuts  off  almost  completely  the  excess  of  rubber 


that  has  squeezed  up  past  it.  An  excellent  modifi- 
cation of  the  mould  is  shown  in  the  cut.  The 
upper  part  with  parallel  sides  serves  as  a guide  for 
the  plunger.  It  is  a similar  extension  as  the  one 
recommended  to  be  used  for  the  plunger  in  the  hol- 
low pencil  and  chair  leg  tip  moulds  just  spoken  of. 

Mats. — These  may  generally  be  made  in  the  hot 
press.  Designs  for  them  in  great  variety  may  be 
found  in  cut  glass  and  pressed  glass  dishes,  Many 


92 


RUBBER  HAND  STAMP  MAKING 


of  these  have  patterns  on  their  bottoms  that  can  be 
moulded  in  plaster  to  serve  as  matrices. 

Cord,  Thread  and  Seamless  Tube. — By  placing  the 
mixed  india  rubber  in  a cylindrical  mould  fitted 
with  piston  and  with  one  or  more  round  holes  in  the 
bottom,  the  material  may  be  softened  by  heat  and 
forced  out  of  the  holes  by  depressing  the  piston. 
This  will  form  cylindrical  thread  or  cord.  As  it 
descends  it  may  be  received  in  a box  of  powdered 
talc  and  be  afterwards  cured.  By  providing  the 
hole  with  a mandrel  seamless  tubing  may  be  thus 
made.  In  making  such  the  mandrel  usually  re- 
mains in  place  during  the  curing.  Plenty  of 
powdered  talc  must  be  used. 

Skeletonized  Leaves  as  Models. — These  would  form 
interesting  models  from  which  matrices  could  be 
made  in  plaster.  It  would  be  possible  to  produce 
some  very  pretty  stamps  or  mats  from  these  and 
similar  models. 

After  some  experience  inspection  of  any  article 
will  show  how  it  was  moulded.  The  fin  will  indi- 
cate the  joint  in  the  mould,  and  with  this  as  a clew 
the  mould  can  be  almost  certainly  constructed  like 
the  original. 

India  Rulher  Bulbs. — Bulbs  and  hollow  articles 
generally,  such  as  dolls,  toys  and  the  like,  cannot 
be  made  without  special  high  pressure  hollow 
moulds.  The  general  process  consists  in  cutting 
out  gores  from  mixed  sheet  as  for  a balloon.  The 
edges  are  coated  with  cement  (thick  benzole  or  car- 


AND  THE  MANIPULATION  OF  RUBBER.  93 


bon  disulphide  india  rubber  solution)  and  while 
the  rubber  is  warm  the  seams  are  pressed  and 
knitted  together  with  the  fingers.  A hole  is  left  in 
one  place  through  which  some  pure  water  or  water 
of  ammonia  is  introduced.  The  bulb  is  now  blown 
up  with  the  mouth  or  otherwise,  and  while  inflated 
the  hole  is  pressed  shut.  This  is  often  done  with 
the  teeth.  Any  projections  around  the  seams  are 
cut  off  with  curved  scissors.  The  mould  is  of  iron 
and  in  two  halves.  Powdered  talc  is  applied,  and 
the  bulb  is  placed  in  and  shut  up  in  the  mould 
which  it  should  exactly  fill.  The  mould  is  clamped 
together  and  the  whole  is  put  into  a vulcanizer,  and 
the  rubber  is  cured.  The  steam  and  vapor  formed 
by  its  liquid  contents  expand  it  and  press  it  with 
great  force  against  the  sides  of  the  mould.  After 
curing  the  mould  and  bulb  are  removed  from  the 
vulcanizer,  cooled  by  a shower  bath  of  cold  water, 
the  mould  is  023ened  and  the  bulb  is  removed.  Often 
an  iron  pin  is  left  projecting  through  the  side  during 
the  vulcanizing,  which  pin,  when  withdrawn,  leaves 
the  necessary  aperture,  or  it  is  perforated.  The  bulbs 
are  polished  by  tumbling  in  a revolving  cylinder. 
Considerable  skill  and  practice  are  needed  to  succeed 
in  making  hollow  bulbs.  Great  accuracy  is  needed 
in  cutting  out  the  gores  and  in  joining  the  seams. 


CHAPTER  X. 


THE  MANIPULATION  OP  MASTICATED  SHEET  RUBBER. 

The  manipulation  of  pure  sheet  rubber  is  simple, 
yet  is  liable  to  lead  to  disappointment.  When  two 
pieces  are  laid  face  to  face  and  cut  across  with  a 
sharp  knife,  or  scissors,  the  edges  will  adhere  with 
considerable  tenacity.  This  may  be  increased  by 
applying  some  thick  solution  of  india  rubber  in  a 
Volatile  solvent,  and  by  manipulating  the  sheets  so 
as  to  bring  the  entire  surfaces  of  the  cuts  together. 
Finally  the  material  may  be  charged  with  sulphur 
by  absorption  or  by  Parkes"*  process,  and  cured  in 
a glycerine  or  calcium  chloride  bath,  all  of  which 
are  described  in  chapter  XI.  The  same  treat- 
ment will  affect  the  cement  used  in  making 
the  joint  also,  bringing  about  its  vulcaniza- 
tion. 

Such  in  a few  words  is  the  main  process  in  the 
treatment  of  this  class  of  goods.  Where  it  is  de- 
sired to  prevent  adherence,  soapy  water  or  powdered 
talc  is  used. 

Adherence  may  be  produced  between  the  surfaces 
of  the  sheets  if  they  are  clean,  by  pressure  and  a 
little  warmth,  The  method  of  making  toy  balloons 


THE  MANIPULATION  OF  RUBBER. 


95 


will  give  an  example  of  how  the  article  is  dealt  with 
by  the  manufacturer. 

A pile  of  pieces  of  masticated  sheet  rubber  is 
made.  Every  piece  has  one  side  coated  with  pow- 
dered talc,  and  two  talc-coated  sides  are  placed  in 
contact  in  each  pair.  As  they  are  piled  up,  the 
outer  surfaces  of  each  pair  are  moistened  with 
water.  A steel  punch  or  die,  pear  shaped  in  out- 
line, is  used  to  cut  down  through  the  pile,  cutting 
all  the  pieces  into  that  shape. 

The  pile  is  then  taken  apart  in  pairs.  The  separa- 
tion takes  place  between  the  wet  surfaces,  the  edges 
of  each  pair  adhering  slightly  so  as  to  enclose  the 
talc-coated  surfaces.  The  neck  is  opened  if  neces- 
sary. A rather  weak  or  thin  solution  of  india  rub- 
ber iu  benzole  is  now  brushed  over  the  freshly  cut 
edges.  By  pulling  out  the  centre  of  each  piece  the 
edges  are  brought  into  contact,  and  adherence  is 
produced. 

If  the  Parkes  process  of  vulcanizing,  chapter  XI., 
is  employed  they  are  cured  to  the  slight  extent  nec- 
essary upon  a tray  coated  with  talc.  The  balloons 
are  then  ready  for  inflation. 

They  are  rather  delicate  articles  to  make  except 
for  immediate  use  as  the  thin  material  is  liable  to 
become  over  vulcanized. 

In  the  chemical  laboratory  sheet  rubber  can  be 
used  for  covering  the  ends  of  glass  stirring  rods. 
These  answer  very  nicely  for  cleaning  out  from 
beakers  the  last  particles  of  a precipitate.  The 


96 


BUBBEB  HAND  STAMP  MAKING. 


sheet  is  cut  of  proper  size  and  is  bent  around  the 
end  of  the  rod  and  cut  off  close  with  a pair  of  scis- 
sors. It  adheres  where  cut.  It  is  then  pinched 
with  the  fingers  to  bring  the  edges  into  better  con- 
tact and  the  operation  is  complete.  A slight  heat 
makes  it  adhere  better. 

To  connect  glass  tubes  in  setting  up  laboratory 
apparatus  the  same  material  was  formerly  used.  It 
was  wrapped  around  the  Joint,  tied  with  thread  and 
slightly  warmed.  At  present  this  form  of  connec- 
tion is  wholly  displaced  by  ready  made  rubber 
tubing. 

It  is  interesting  to  observe  in  all  articles  made 
from  this  sheet  the  marks  of  the  original  cutting 
knife.  These  may  be  observed  in  inflated  balloons, 
as  parallel  lines  running  all  over  the  surface,  and 
magnified  by  the  expansion  due  to  the  infiation. 


CHAPTER  XL 


VARIOUS  VULCAKIZIKG  AKD  CURING  METHODS. 

The  regular  methods  of  vulcanizing  and  curing 
can  be  departed  from  and  good  results  obtained. 
A few  excellent  methods  differing  essentially  from 
the  ordinary  ones  are  described  which  will  be  of 
service  to  workers  on  the  small  scale,  as  they  enable 
one  to  dispense  with  vulcanizer  and  air  bath  en- 
tirely. 

One  type  of  curing  process  does  away  with  the  air 
or  steam  vulcanizer,  and  substitutes,  as  the  curing 
agency,  a hot  bath  of  liquid.  For  this  purpose  a 
fluid  is  required  that  will  not  act  injuriously  upon 
the  India  rubber,  and  which  will  give  a curing 
temperature  without  boiling  away.  One  favorite 
liquid  is  glycerine.  This  can  be  heated  to  the  nec- 
essary degree  and  is  an  excellent  substitute  for  the 
expensive  apparatus  often  used.  For  experimental 
work  it  is  exceedingly  convenient. 

In  use  it  is  placed  in  a vessel  of  proper  size 
and  a thermometer  is  suspended  so  that  its  bulb 
dips  into  the  liquid  near  one  side  and  does  not 
touch  the  bottom  of  the  vessel.  The  heat  is  applied 
by  a gas  burner,  alcohol  lamp  or  oil  stove.  Of 


98 


RUBBER  HAND  STAMP  MAKING 


course  the  vessel  may  be  placed  on  an  ordinary 
cooking  stove  or  range,  and  the  heat  may  be  gradu- 
ated and  adjusted  by  moving  it  about  until  it 
reaches  a part  of  the  stove  where  the  proper  heat 
will  be  maintained. 

The  mould  with  its  contents  is  immersed  in  the 
glycerine,  care  being  taken  to  see  that  it  so  placed 
as  to  assume  the  mean  temperature  of  the  liquid 
and  not  to  be  heated  too  hot.  This  might  happen 
if  it  stood  on  the  bottom  of  the  vessel,  so  it  is  well 
to  have  it  supported  or  suspended  a little  above 
it. 

It  is  easy  to  see  that  the  whole  may  be  so  arranged 
that  the  screw  handle  or  pressure  nuts  of  the  mould 
will  rise  above  the  liquid.  In  this  case  the  press 
can  be  screwed  down  while  the  article  is  heating. 

Instead  of  glycerine  a strong  solution  of  some 
salt  in  water  has  been  recommended.  A solution 
of  calcium  chloride,  or  some  other  salt  can  be  sub- 
stituted. Either  are  very  cheap  and  will  be  quite 
satisfactory. 

Another  treatment  which  applies  also  to  the  mixing 
operation  is  by  the  sulphur  bath.  Sulphur  is  melted 
in  an  iron  vessel  and  brought  to  a temperature  of 
248°  F.  (120°  C.).  A piece  of  unmixed  pure  caout- 
chouc immersed  in  this  bath  will  gradually  absorb 
sulphur.  The  case  is  almost  parallel  with  the 
absorption  of  water  or  benzole  by  the  gum.  The 
piece  swells  and  thickens  as  it  is  acted  on  and 
eventually  will  contain  enough  sulphur  for  vulcani- 


AND  THE  MANIPULATION^  OF  RUBBER.  99 


zation.  It  may  absorb  as  much  as  fifty  per  cent. 
The  point  of  proper  absorption  must  be  settled 
more  or  less  empirically  or  by  successive  trials. 

After  enough  has  been  taken  up  the  piece  is  re- 
moved and  dipped  into  cold  water,  which  cracks  the 
adherent  sulphur  so  that  it  can  be  brushed  or  rubbed 
off.  This  gives  a piece  of  mixed  rubber  ready  for 
moulding  and  curing.  It  can  be  heated  and 
moulded  and  may  be  cured  as  desired,  in  a liquid 
bath,  hot  press  or  vulcanizer. 

It  will  be  observed  that  this  provides  for  the  ad- 
mixture of  sulphur  only;  no  talc  or  other  solid  can 
be  thus  introduced.  The  addition  of  these  solids 
tends  to  make  the  rubber  of  a more  attractive  color 
and  their  use  is  not  to  be  deprecated  in  all  cases. 
Hence  the  sulphur  bath  process  is  not  to  be  consid- 
ered a perfect  one. 

In  the  sulphur  bath  the  mixing  and  curing 
processes  can  be  combined.  If  the  liquid  sulphur  is 
heated  to  the  vulcanizing  temperature,  284°  F. 
(140°  C.),  a thin  strip  of  gnm  immersed  in  it  will 
be  vulcanized  completely  in  a few  minutes.  A 
heating  of  several  hours  at  the  lower  temperature’ 
will  effect  the  same  result. 

The  sulphur  bath  processes  must  be  regarded  as 
unsatisfactory.  It  is  not  easy  to  feel  that  any  de- 
pendence can  be  placed  upon  them  as  regards  re- 
liability or  constancy  of  product.  The  sulphur  also 
will  mostly  effect  the  surface.  Thin  pieces  may  be 
satisfactorily  treated,  but  the  same  confidence  can- 


100 


RVBBBR  HAND  STAMP  MAKING 


not  be  felt  as  is  experienced  when  specific  amounts 
of  ingredients  have  been  mixed  in  with  pure  caout- 
chouc in  a regular  mixing  machine. 

The  sulphur  bath  is  of  value  to  the  experimenter, 
enabling  him  to  do  his  own  mixing  without  expen- 
sive apparatus. 

Bromine,  iodine,  chlorine  and  nitric  acid  are  vul- 
canizers.  A piece  of  sheet  rubber  dipped  into 
liquid  bromine  is  instantly  vulcanized.  Iodine  and 
nitric  acid  have  also  been  used  in  . commercial 
work. 

Alkaline  or  alkaline  earth  sulphides  can  be  em- 
ployed in  solution  under  pressure  for  vulcanizing. 
At  a vulcanizing  temperature  their  solutions  will 
answer  for  thin  sheet  very  well.  Polysulphides  of 
calcium  have  thus  been  employed. 

By  simply  lying  embedded  in  finely  divided  sul- 
phur at  a temperature  of  233°  F.  (112°  C.)  as  much 
as  ten  per  cent,  of  sulphur  may  be  absorbed  by  thin 
sheet  rubber.  This  is  one  of  the  processes  pecul- 
liarly  suited  for  work  on  the  small  scale.  It  ‘may  be 
used  instead  of  the  Parkes  process  next  to  be  de- 
scribed. 

Chloride  of  sulphur  is  an  orange  red  mobile 
liquid  of  a peculiar  and  disagreeable  odor.  It  boils 
at  276°  F.  (136°  0.).  It  dissolves  both  sulphur  and 
chlorine  so  that  it  is  not  easy  to  obtain  it  in  a pure 
state.  If  unmixed  india  rubber  is  exposed  to  its 
action  it  will  quickly  become  vulcanized.  At  ordi- 
nary temperatures  the  mixing  action  takes  place. 


AND  THE  MANIPULATION  OF  RUBBER.  101 


though  it  is  much  accelerated  by  a slight  applica- 
tion of  heat. 

It  is  quite  possible  that  this  action  may  be  of  use 
to  the  reader  in  his  manipulation  of  pndia  rubber. 
Thin  sheet  may  be  vulcanized  by  being  immersed  in 
a solution  of  this  substance  in  bisulphide  of  carbon 
followed  by  slight  heating.  The  thin  layer  of 
caoutchouc  left  by  evaporation  of  the  chloroform 
solution  of  india  rubber  may  thus  be  vulcanized  so  as 
to  become  comparatively  strong  and  elastic.  Where 
the  same  solution  has  been  used  as  a cement  or  for 
patching  overshoes  and  finishing  the  patch,  a vul- 
canization can  thus  be  given  to  it. 

The  process  is  known  as  Parkes^  cold  curing  pro- 
cess. 

A solution  of  one  part  of  chloride  of  sulphur  in 
forty  parts  of  bisulphide  of  carboil  is  of  good 
strength  for  rapid  work.  A thin  article  needs  but  an 
instant  of  immersion.  It  then  is  placed  in  a box  or 
tray  upon  some  talc  powder  and  is  heated  to  about 
104°  F.,  (40°  0.).  One  minute  of  curing  will  suf- 
fice. It  is  advisable  to  wash  off  the  articles  after- 
wards in  water  or  in  weak  lye  to  remove  any  traces 
of  acid. 

Petroleum  naptha  can  be  used  as  the  solvent  in- 
stead of  bisulphide  of  carbon.  The  latter  substance 
has  an  exceedingly  disagreeable  odor,  and  its  vapors 
must  be  considered  rather  injurious  especially  to 
those  who  are  not  accustomed  to  them. 

When  thick  articles  are  to  be  cured  by  this  pro- 


102 


BUBBEU  HAND  STAMP  AIAKINQ. 


cess  a much  more  diluted  solution  is  used.  One 
per  cent,  or  less  of  the  chloride  of  sulphur  is  the 
proportion  used.  The  object  of  this  is  to  enable 
a longer  immersion  to  be  employed  so  that  the  in- 
terior will  be  affected  before  the  outer  layers  become 
too  much  charged  with  the  vulcanizing  material. 

In  this  short  description  of  the  Parkes  curing 
process  hints  for  a useful  method  may  be  found. 
The  process  is  beyond  doubt  by  far  the  simplest 
known  for  treatment  of  India  rubber.  Exactly 
what  reaction  takes  place  is  unknown.  Whether 
the  sulphur  or  the  chlorine  is  the  acting  vulcanizer 
has  not  as  yet  been  determined. 

Its  defect  is  that  it  produces  surface  action,  anal- 
ogous to  casehardening.  One  method  of  avoiding 
this  is  to  remove  the  articles  from  the  sulphur 
chloride  bath  and  at  once  to  immerse  them  in  water. 
This  prevents  the  rapid  volatilization  of  the  solvent 
and  an  equalizing  of  the  absorption  ensues. 


CHAPTER  XII. 


THE  SOLUTION  OF  INDIA  RUBBER. 

India  rubber  presents  some  difficulties  in  its 
solution.  If  a piece  of  pure  gum  just  as  received  by 
the  factory  is  placed  in  hot  water  it  will  swell  and 
whiten  after  a while,  but  will  not  dissolve.  If  a 
similar  piece  is  placed  in  benzole  a similar  but 
greatly  exaggerated  action  takes  place.  The  piece 
if  left  to  soak  for  a day  or  more  swells  enormously, 
but  very  little  solution  is  effected. 

The  swollen  India  rubber  can  be  removed  from 
the  benzole  in  a single  piece.  It  will  display  all  the 
layers  and  marks  of  the  original  piece  which  was 
perhaps  of  not  one  hundredth  part  of  its  volume. 
Some  parts  will  be  a perfect  transparent  jelly. 

It  has  been  found  that  masticated  india  rubber 
dissolves  with  comparatively  little  difficulty.  If 
the  experimenter  will  place  in  a porcelain  mortar, 
the  jelly-like  mass  obtained  as  above  detailed,  and 
will  rub  it  up  thoroughly,  it  will  be  effectually  mas- 
ticated. This  requires  a little  patience,  as  the 
slippery  material  seems  to  elude  the  pestle.  Yet 
eventually  it  will  all  be  reduced  to  a perfectly  homo- 
geneous mass.  Its  action  while  being  rubbed  up  is 


104  RUBBER  HAND  STAMP  MAKING 

very  peculiar.  At  first  no  progress  seems  to  be 
made.  After  a little  the  lumps  yield  to  the  friction. 
The  rubber  then  begins  to  attach  itself  to  the  pestle 
and  mortar,  and  begins  to  be  drawn  out  into  ever 
changing  webs  and  threads.  As  the  operation  ap- 
proaches completion  the  material  makes  a snapping, 
crackling  noise  familiar  to  all  rubber  workers. 
When  complete  there  will  be  no  lump  left,  and  the 
whole  will  be  a uniform  pulp. 

If  benzole  or  a volatile  solvent  has  been  used,  the 
rubber  will  easily  be  removed  from  the  mortar  with 
a spatula  or  palette  knife.  If  turpentine  was  the 
solvent  it  will  be  impossible  to  remove  the  last 
traces  except  after  long  standing  or  by  solution. 

If  replaced  in  the  original  solvent  it  will  now  come 
into  nearly  or  quite  perfect  solution.  This  is  the 
best  way  of  masticating  on  the  small  scale.  It  is 
almost  impossible  to  masticate  untreated  gum  in  an 
ordinary  mortar. 

The  dealers  sell  a special  india  rubber  for  the 
manufacture  of  cement  and  solutions.  This  is  so 
treated  by  mastication  that  it  dissolves  with  great 
readiness.  It  is  also  said  that  heating  under  pres- 
sure is  used  to  dissolve  it  in  some  factories. 

Many  solvents  have  been  used  and  none  work 
without  some  difficulty.  Benzole,  coal  tar  naptha, 
petroleum  naptha,  carbon  disulphide,  ether  and 
chloroform,  oil  of  turpentine  and  caoutchoucin  are 
the  best  known.  The  naptha  best  suited  for  its 
solution  is  termed  solvent  naptha.  It  has  a specific 


AND  THE  MANIPULATION  OF  PUBBEB.  105 


gravity  of  .850  at  60°  F.  (15^°  C.);  it  boils  at  from 
240°  F.  (11514^  C.)  to  250°  F.  (121°  C.)  and  on  evap- 
oration should  leave  no  more  than  ten  per  cent,  of 
residue  at  320°  F.  (160°  C.) 

Payen  recommends  a mixture  of  95  parts  bisulph- 
ide of  carbon  with  5 parts  of  absolute  alcohol. 

Commercial  chloroform  is  apt  to  be  too  impure  to 
act  as  a good  solvent.  It  is  apt  to  contain  alcohol 
mixed  with  it  as  a preservative,  which  impairs  its 
effectiveness. 

Some  of  these  solutions  are  better  suited  than 
others  for  the  deposition  of  thin  layers  by  evapora- 
tion. Turpentine  gives  a very  sticky  and  unman- 
ageable solution,  which  dries  very  slowly.  Payen^s 
solution  and  the  chloroform  and  the  benzole  solu- 
tions may  be  cited  as  especially  adapted  for  this 
purpose.  Careful  vulcanization  by  the  cold  curing 
method  can  be  applied  to  articles  made  by  such 
deposition  from  evaporation. 

In  the  case  of  all  of  them  some  form  of  mastication 
for  the  india  rubber  is  needed.  The  simple  mortar 
grinding  of  the  gum  swelled  by  the  solvent  is  the 
only  practical  treatment  without  special  apparatus. 

When  it  is  remembered  that  fixed  oils  are  de- 
stroyers of  vulcanized  or  unvulcanized  india  rubber 
it  will  be  obvious  how  important  it  is  to  use  pure 
solvents.  Too  great  care  cannot  be  taken  to  pre- 
serve the  liquids  pure  and  free  from  such  matter. 

A solid  hydrocarbon  may  be  used.  Thus  paraffin 
wax,  such  as  candles  are  made  of,  when  melted  acts 


106 


BUBBEB  HAND  STAMP  MAKING 


as  a solvent.  The  resulting  liquid  solidifies  when  it 
cools,  retaining  an  almost  greasy  feel. 

Boiling  oil  of  turpentine  is  recommended  hy 
some  for  the  solution  of  vulcanized  india  rubber. 
Phenyle  sulphide,  it  is  stated,  will  soften  it  so  as  to 
render  it  workable.  The  latter  discovery  is  credited 
to  Dr.  Stenhouse. 

It  is  stated  that  a solution  or  pasty  mixture  of 
one  part  of  caoutchouc  in  eleven  parts  of  turpentine 
with  one  half  part  of  a hot  concentrated  solution  of 
sulphur  (potassium  sulphide)  gives  on  evaporation  a 
film  neither  tacky  nor  soft,  a species  of  vulcaniza- 
tion taking  place. 

It  is  of  much  interest  to  note  that  an  aqueous 
solution  of  india  rubber  has  been  proposed  in  which 
the  vehicle  is  a solution  of  borax  in  water.  This  is 
well  known  to  be  a solvent  for  shellac  and  other 
resins.  It  has  been  recommended  often  as  a vehicle 
for  rubbing  up  india  ink.  The  ink  made  by  mixing 
lampblack  with  the  shellac  solution  is  nearly  water- 
proof. A shellac  varnish  is  given  by  the  plain  solu- 
tion. 

The  experiments  upon  india  rubber  were  pub- 
lished in  a recent  trade  paper.  One  method  of 
making  the  solution  is  as  follows. 

A solution  of  borax  two  fifths  saturated  is  made 
by  adding  to  two  volumes  of  saturated  solution 
three  volumes  of  water.  To  this  is  added  a solution 
of  india  rubber  in  benzole  or  other  hydrocarbon  of 
such  strength  and  in  such  quantity  as  to  contain 


AND  THE  MANIPULATION  OF  RUBBEB.  107 


from  three  and  one-half  to  four  and  one-half  per 
cent,  of  India  rubber  referred  to  the  borax  solution. 
It  is  now  vigorously  shaken  and  heated  to  120°-140° 
F.  (49°-60°  0.)  and  the  agitation^  not  too  violent,  is 
continued  until  it  cools.  Oeara  or  Madagascar  rub- 
ber answers  best;  Para  is  not  so  good  for  this  for- 
mula. This  may  be  termed  the  indirect  or  emul- 
sion method. 

For  direct  solution  from  two  to  three  volumes  of 
water,  may  be  added  to  three  volumes  of  saturated 
borax  solution.  The  india  rubber  is  added  in  ex- 
tremely thin  shavings  and  the  solution  is  heated. 
For  weak  solutions  the  boiling  point  need  not  be 
reached.  For  strong  solutions  the  heating  should 
be  done  under  pressure  so  as  to  bring  up  the  pres- 
sure to  one  to  three  atmospheres. 

Such  solutions  may  contain  as  much  as  eight  per 
cent,  of  the  gum.  The  mixture  is  liable  to  coagu- 
late or  gelatinize  just  at  the  wrong  time,  but  it  may 
be  of  value  as  a vehicle  or  as  a waterproofing  agent. 
It  deserves  further  investigation,  which  it  is  to  be 
hoped  it  will  duly  receive. 

Great  care  is  necessary  in  working  with  naptha, 
benzole,  carbon  disulphide  and  similar  liquids. 
Their  vapor  is  given  off  at  ordinary  temperatures 
and  may  travel  some  distance  to  a lamp  or  fire  and 
become  ignited  and  carry  the  flame  back  to  the  ves- 
sel. Their  vapors  are  also  anaesthetic  and  should  be 
avoided  as  regards  inhalation. 


CHAPTEE  XIII. 


EBONITE,  VULCANITE  AND  GUTTA-PERCHA. 

Ebonite  and  Vulcanite. — These  two  well  known 
substances  are  India  rubber,  in  which  the  vulcaniza- 
tion process  has  been  intensified.  From  twenty- 
five  to  fifty  per  cent,  of  sulphur  is  added  in  the 
mixing,  and  the  curing  is  prolonged  to  several 
hours.  ' A temperature  of  275°  F.  (135°  C.)  for  six 
to  ten  hoars  is  sometimes  recommended,  but  gener- 
ally a shorter  period  at  the  regular  temperature, 
284°  F.  (140°  0.),  may  be  employed. 

The  mixed  sheet  is  made  and  sold  extensively  for 
dentists^  use.  It  is  soft  and  fiexible  and  very  easily 
moulded.  It  is  treated  like  the  regular  mixed  sheet 
in  every  respect,  except  that  plumbago  brushed  on 
the  slightly  oiled  surface  of  the  mould  is  recom- 
mended instead  of  the  light  colored  talc,  to  prevent 
adherence.  Wax  where  available  is  better  than 
oil. 

Sometimes  specimens  are  built  up  in  sections. 
About  an  hour  before  full  vulcanization  in  the 
fourth  stage,  new  material  can  be  added  and  will 
attach  itself  to  the  old.  The  stages  of  vulcaniza- 
tion are  thus  given  by  Bolas. 


AND  THE  MANIPULATION  OF  RUBBER.  109 


Several  distinct  stages  or  steps  may  be  traced 
during  the  curing  of  ebonite;  and  I wish  to  call 
your  attention  to  some  specimens  illustrating  these 
various  stages. 

‘‘Here,  in  the  first  place,  is  the  plain  mixture  of 
sulphur  and  rubber,  this  being  nearly  white,  and 
capable  of  becoming  quite  plastic  or  soft  by  the  ap- 
plication of  a gentle  heat. 

“ The  second  specimen  illustrates  the  action  of  a 
very  moderate  degree  of  heat  on  the  mixed  material, 
this  particular  sample  having  been  heated  to  128° 
Centigrade  for  twenty  minutes.  It  is,  as  you  see, 
somewhat  darkened,  and  has  lost  a little  of  its  orig- 
inal softness;  while  a degree  of  heat  which  would 
have  rendered  the  original  mixture  plastic,  like 
putty,  fails  to  make  much  impression  upon  it. 

“ The  third  specimen  illustrates  the  effect  of  a 
more  prolonged  heating,  this  sample  having  been 
heated  for  an  hour  to  135°  Centigrade.  It  is  olive 
green  in  color,  and  has  acquired  a certain  amount 
of  elasticity,  resembling  that  of  a rather  inferior 
quality  of  vulcanized  caoutchouc. 

“ The  fourth  stage  of  curing  is  illustrated  by  this 
specimen,  which  you  see  is  brown,  and  tolerably 
hard.  Ebonite  in  this  state  refuses  altogether  to 
become  plastic  by  heat,  and  a temperature  of  150° 
maintained  for  half  an  hour  or  less  would  suffice  to 
bring  it  to  the  fifth  stage,  or  that  of  finished 
ebonite. 

“The  fifth  stage,  or  that  of  properly  cured 


110 


RUBBER  HAND  STAMP  MAKING 


ebonite,  is  the  goal  to  be  arrived  at  in  manufactur- 
ing the  material.  There  should  be  no  places  where 
the  curing  is  imperfect,  a kind  of  defect  which  is 
likely  to  happen  when  articles  of  unusual  thickness 
are  vulcanized,  and  no  portion  of  the  ebonite  should 
be  spongy  or  honeycombed  by  air  bubbles. 

The  sixth,  or  spongy  state,  is  generally  the 
result  of  over-heating,  bubbles  of  gas  forming  in 
the  material,  and  converting  it  into  a kind  of 
porous,  cinder-like  mass. 

specimen  will  now  be  handed  round,  which 
illustrates  the  third,  fourth,  fifth  and  sixth  stages, 
as  already  described.  The  specimen  in  question 
was  cured  on  a hot  plate,  this  having  probably  been 
heated  to  160°  or  170°  Centigrade;  and  you  will  be 
able  to  trace  all  gradations  in  the  curing  operation, 
from  the  first  setting  of  the  plastic  material  to  the 
destruction  of  the  ebonite  by  overheating.” 

Cement  for  uniting  pieces  of  the  partially  cured 
material  may  be  made  by  rubbing  up  some  of  the 
untreated  scrap  with  benzole. 

At  the  heat  of  boiling  water,  ebonite  can  be  bent 
to  a certain  extent,  which  bend  it  retains  on  cooling. 
When  warm  an  impression  of  a coin  or  relief  die 
may  be  made  on  it  by  heavy  pressure  which  it  will 
retain.  On  heating  the  image  disappears.  If  before 
heating  the  surface  is  planed  off  and  the  piece  is 
heated  the  image  formerly  in  intaglio  will  expand 
into  relief. 

By  the  exact  process  of  rubber  stamp  making 


AND  THE  MANIPULATION  OF  RUBBER.  Ill 


excellent  stereotype  plates  may  be  made  of  eb- 
onite. 

It  can  be  turned  at  high  speed  in  a lathe  and  pol- 
ished with  fine  000  emery  paper  followed  by  a cloth 
bob  with  rotten  stone,  etc.,  and  water  or  oil.  Blot- 
ting paper,  charged  with  the  above  or  with  tripoli, 
is  excellent  for  polishing  small  surfaces  by  hand. 

Ebonite  is  a good  connecting  material  between 
softer  rubber  and  iron,  the  whole  being  vulcanized 
together  ; the  iron  should  be  well  roughened  or 
cut  into  rasp-like  or  file-like  projections. 

Ebonite  is  properly  the  name  for  black  hard  rub- 
ber, and  vulcanite  for  the  colored  products  such  as 
used  by  dentists  and  others. 

GUTTA-PERCHA. 

Gutta-percha  is  prepared  by  coagulation  from  the 
juice  or  sap  of  several  trees,  among  others  the 
Isonandra  gutta,  of  Borneo  and  the  East  Indian 
Archipelago.  The  product  gutta-percha  is  iden- 
tical in  composition  with  india  rubber.  It  is  hard 
at  all  ordinary  temperatures. 

Its  manufacture  includes  purification  and  masti- 
cation. It  is  far  more  amenable  to  treatment  than 
is  india  rubber.  Many  materials  are  mixed  with  it 
as  adulterants  or  otherwise  in  the  factories. 

It  is  more  useful  in  the  form  of  sheets.  These 
when  heated  to  122°  F.  (50°  C.)  become  pliable  and 
can  be  moulded  by  pressure  to  any  degree.  At  the 


112 


RUBBER  HAND  STAMP  MAKING 


temperature  of  boiling  water  it  becomes  pasty  and 
adhesive,  and  at  266°  F.  (130°  0.)  it  is  so  soft  that  it 
may  be  considered  as  melted. 

It  is  an  admirable  moulding  material.  Stereo- 
types and  other  relief  or  intaglio  images  can  be 
made  by  pressing  it  while  heated.  These  are  often 
absolutely  perfect  reproductions  of  the  original. 

Dishes  for  photographic  purposes,  etc.,  are  easily 
made  out  of  the  sheet.  By  gentle  warming  they 
become  pliable,  and  a greater  heat  makes  surfaces 
capable  of  adhering  by  pressure. 

Tubes  can  be  made  by  the  squirting  process,  as 
used  for  india  rubber.  Wires  are  coated  with  it  in 
a similar  manner. 

It  has  several  defects.  It  is  not  durable  if  ex- 
posed to  the  air  with  consequent  changes  of  temper- 
ature. It  is  also  too  easily  softened  by  heat,  as  of 
course  no  hot  liquid  can  be  introduced  into  a gutta- 
percha vessel.  The  Parkes  cold  curing  process  can 
be  applied  to  it,  which  makes  it  more  indifferent  to 
heat.  This  is  applied  by  dipping  an  instant  and 
drying.  After  several  repetitions  the  period  of  dip- 
ping is  prolonged  and  ultimately  it  is  left  immersed 
some  time.  If  left  immersed  at  first  it  would  dis- 
solve. 

It  is  soluble  in  most  caoutchouc  solvents,  particu- 
larly in  carbon  disulphide. 


CHAPTER  XIV. 


GLUE  OR  COMPOSITION  STAMPS. 

Stamps  made  from  a mixture  of  glue,  glycerine, 
and  molasses  or  from  similar  mixtures  are  u^n  excel- 
lent substitute  for  india  rubber  stamps.  Properly 
made  they  possess  all  the  flexibility  that  character- 
izes the  rubber  ones,  while  for  fatty  inks  such  as  that 
used  by  printers  and  lithographers,  which  inks  tend 
to  destroy  rubber  stamps,  they  are  much  better. 
They  are  adopted  by  the  United  States  government 
for  making  dating  stamps  for  use  in  the  Post  Office 
Department  ; by  publishers  of  directories  for  print- 
ing advertisements  on  the  edges  of  their  publica- 
tions, and  in  many  other  cases.  Our  description 
shall  follow  as  closely  as  possible  the  process  and 
methods  used  in  the  United  States*  Post  Office. 
They  are  there  termed  ^^composition  blotters.'’^ 

The  composition  of  which  they  are  made  is  print- 
er^’s  roller  material.  Nine  and  one-half  pounds  of 
fine  quality  glue  are  soaked  in  just  enough  soft 
water  to  cover  it  until  it  is  thoroughly  softened. 
It  is  then  melted.  In  the  Government  Department 
a steam  kettle  is  provided  for  the  purpose.  An 
ordinary  glue  pot  will  answer  for  smaller  quantities. 


114 


RUBBER  HAND  STAMP  MAKING 


Wlien  melted  four  and  one-half  pounds  of  best  molas- 
ses and  seven  pounds  of  glycerine  are  added^  and  the 
whole  is  thoroughly  mixed.  The  formula  varies  a 
little  according  to  the  prevailing  temperature,  less 
molasses  being  added  when  the  weather  is  warm,  and 
vice  versa.  Experience  is  here  the  best  teacher. 
When  well  mixed  it  is  poured  out  into  tin  pails 
whose  inner  walls  or  sides  and  bottom  have  been 


rubbed  over  with  oil.  It  solidifies  in  cooling  and 
becomes  a clear  brown  jelly  quite  free  from  any 
stickiness  or  superficial  moistness. 

In  use  it  is  turned  out  of  the  pails  to  which, 
owing  to  the  oiling,  it  does  not  adhere.  It  is  cut 
off  as  wanted,  melted  by  heat  and  cast  in  oiled 
moulds. 

The  latter  are  made  of  type  metal  to  which  one- 
third  its  weight  of  lead  has  been  added.  As  model 


AND  THE  MANIPULATION  OF  RUBBER.  Il5 

for  the  mould  or  matrix  a brass  model  of  the 
stamp  is  employed.  This  represents  a sort  of  oval 
based  cut-off  or  truncated  cone,  about  an  inch 
high  and  a little  over  an  inch  long  on  its  base.  A 
flange  extends  outward  from  its  base  and  a tube  is 
provided  to  fit  this  flange.  Its  smaller  end  corre- 
sponds to  the  face  of  the  stamp,  and  on  it  are  en- 
graved in  full  relief  any  permanent  characters. 


Composition  Stamp  Mould. 

circles  or  border  lines,  etc.  Through  its  centre  one 
or  more  apertures  are  made.  Into  these,  changeable 
steel,  iron  or  brass  type  may  be  introduced  and  set 
fast  with  plaster  of  paris. 

To  make  the  mould,  the  brass  model  witli  its  mov- 
able type  set  as  required  is  placed  upon  a flat  table 
or  plate,  face  upward,  and  surrounded  by  the  tube, 
as  shown  in  partial  section  in  the  cut,  page  114.  The 
tube  is  a strip  of  sheet  iron,  which  is  bent  around  the 
flange  and  is  secured  in  place  by  a wire  twisted 
around  it.  The  melted  alloy  (type,  metal  and  lead)  is 


116 


RUBBER  HAND  STAMP  MAKING 


poured  into  the  space  thus  formed  until  it  rises  a 
quarter  of  an  inch  above  the  face  of  the  model.  In 
a few  minutes  it  sets  and  is  removed  and  allowed 
to  cool.  This  gives  a cup  with  the  inscription  and 
design  depressed  or  in  intaglio  upon  its  inside  base. 
This  is  shown  in  the  cut,  page  115,  partly  in  section; 
it  will  of  course  be  understood  that  the  mould  forms 
a complete  cup. 

To  make  the  stamp  the  interior  surface  of  the 
mould  is  oiled  wdth  a stiff  brush.  It  is  not  material 
what  oil  is  used.  The  composition  melted  by  heat  is 
then  poured  into  the  cup,  and  is  allowed  to  solidify. 
Owing  to  the  conical  shape  of  the  mould  it  is 
readily  removed.  The  mould  must  be  hot  but  not 
too  much  so. 

In  the  Post  Office  stamps  the  date  requires  to  be 
changed  frequently.  Some  of  the  figures  do  duty 
for  two  or  three  days  each  month.  Thus  the  figure 
8 is  in  the  designation  of  three  days,  the  eighth, 
eighteenth,  and  twenty-eighth.  There  are  three 
changes  involved  therefore  in  connection  with  this 
day  numeral.  When  a stamp  mould  or  matrix  is  cast 
the  place  of  numerals  that  are  to  be  changed  is 
filled  with  a blank  space  in  the  part  where  the  type 
would  otherwise  come.  A number  is  stamped  in 
this  space  when  needed,  by  means  of  an  ordinary 
steel  number-punch. 

When  the  number  is  to  be  changed  the  old  char- 
acter is  scraped  or  cut  out,  leaving  a small  irregular 
hollow.  A very  small  piece  of  soft  lead,  about  one- 


AND  THE  MANIPULATION  OF  RUBBER.  117 


sixteenth  of  an  inch  on  each  side,  is  dropped  into 
the  hollow.  With  a flat  faced  punch  it  is  flattened 
out,  and  on  it  the  new  number  is  impressed  by  a 
steel  punch.  This  operation  is  repeated  a great 
many  times  before  the  matrix  is  worn  out. 


In  the  cut,  page  115,  one  number  is  shown  as 
stamped  into  the  soft  lead,  and  at  the  other  end  of 
the  stamp  is  a blank  space  ready  for  a number. 

The  casting  of  a stamp  is  so  extremely  simple 
that  no  attempt  is  made  to  use  movable  type,  as  in 
permanent  rubber  dating  stamps. 

While  it  is  obvious  that  these  composition  stamps 
could  be  attached  directly  to  wooden  handles,  a spe- 


118 


BUBBER  HAND  STAMP  MAKING 


cial  style  of  handle,  shown  in  the  cuts,  is  employed 
by  the  Post  Office.  A wooden  handle  carries  at  its 
end  a brass  base,  to  which  is  pivotted  a swinging 
piece  that  is  perforated  by  a conical  oval  aperture  a 
little  larger  than  the  small  end  of  the  stamjD.  The 
edges  of  this  aperture  are  slightly  rounded. 

It  is  swung  around  as  shown  in  the  first  figure, 
and  the  stamp,  previously  moistened  on  its  sides,  is 
forced  in.  If  the  stamp  is  properly  made  it  is  sur- 
prising how  much  force  may  be  used  to  insert  it.  If 
the  edges  of  the  brass  swinging  piece  are  not  rounded 
there  is  danger  of  the  composition  being  cut.  The 
stamp  in  its  brass  frame  is  then  swung  back  over 
the  brass  base,  where  it  is  secured  by  a catch.  The 
stamp  is  now  ready  for  use,  as  shown  in  the  second 
figure  of  the  cut. 

It  is  imperative  that  no  aqueous  or  glycerine  ink 
be  employed  for  continuous  work  with  such  stamps. 
Common  printers^  ink  is  perfectly  satisfactory,  and 
the  work  may  be  nearly  or  quite  as  good  as  that  ex- 
ecuted by  an  india  rubber  stamp. 

The  Post  Office  manufactures  a pad  for  use  with 
printers’  ink  into  whose  manufacture  the  same  com- 
position enters.  The  ink  retainer  is  a piece  of  fine 
felt,  one-quarter  to  one-half  an  inch  thick.  This  is 
placed  in  the  bottom  of  a shallow  steel  mould,  where 
it  enters  for  half  its  depth  into  a recess  that  it  ac- 
curately fits.  The  composition  from  old  stamps, 
melted  up,  is  then  poured  upon  and  around  it,  the 
mould  being  previously  oiled.  When  it  is  full  a 


AND  THE  MANIPULATION  OF  RUBBER.  119 


piece  of  strong  maiiilla  paper,  of  the  area  of  the  felt 
only,  is  placed  upon  the  bottom  of  the  glne  pad  on 
its  centre,  which  as  it  lies  in  the  mould  is  its  upper- 
most part.  The  paper  adheres  strongly  as  the  glue 
hardens.  Eventually  it  is  turned  out  of  the  mould, 
and  a pad,  shown  in  the  cut,  is  produced.  The 
dotted  lines  show  the  limits  of  the  felt  pad.  The 
glue  composition  underlies,  surrounds  and  extends 
outwards  from  the  felt  portion.  It  is  found  that 
the  elasticity  of  the  composition  makes  the  pad 


much  pleasanter  for  rapid  stamping. 

The  above  description  gives  the  clew  to  making 
any  stamp  of  this  description.  The  matrix  may  be 
of  dental  plaster,  or  of  oxychloride  of  zinc  cement. 
The  mould  may  be  built  up  of  type  of  any  kind. 

The  composition  is  so  cheap  that  the  stamp  can 
be  made  quite  thick.  This  gives  it  a high  degree 
of  elasticity  and  adaptability  to  uneven  surfaces. 
It  may  be  mounted  by  adherence  upon  a flat  board 
or  block,  provided,  if  necessary,  with  handles.  If  the 


120 


HUBBEE  HAND  STAMP  MAKING. 


board  or  block  is  placed  upon  the  composition  while 
it  is  still  warm  and  liquid,  as  it  solidifies  the  board 
and  composition  will  adhere  with  great  tenacity. 

All  moulds  or  surfaces  to  which  it  is  desired  that 
the  melted  composition  shall  not  adhere  must  be 
oiled. 

The  moulds  must  not  be  cold  or  the  composition 
will  not  enter  the  .fine  divisions.  If  on  the  other 
hand  they  are  too  hot  the  mixture  will  adhere. 
Experience  will  teach  the  right  conditions  for  suc- 
cess. 

Below  are  given  other  formulae  for  roller  composi- 
tion. The  formula  already  given  in  this  chapter  is 
that  used  by  the  United  States  Post  Office  Depart- 
ment. 

I.  Old  Home  Keceipt:”  Glue  2 lbs.,  soaked  over 
night,  to  ISTew  Orleans  molasses  1 gallon.  Hot 
durable,  but  excellent  while  it  lasts. 

II.  Glue  lbs.,  molasses  2>^  gal.,  Venice  tur- 
pentine 2 oz.,  glycerine  12  oz.;  mix  as  directed 
above. 


CHAPTER  XV. 

THE  HEKTOGRAPH. 

For  obtaining  multiple  copies  of  writing,  the 
apparatus  called  the  Hektograph  or  Papyrograph 
has  been  extensively  adopted.  In  general  terms  it 
consists  of  a tray  filled  with  a jelly  like  composition. 
Any  imprint  made  upon  the  surface  with  aniline 
ink  can  be  transferred  to  paper  by  simple  pressure. 
The  tray  filled  with  composition  is  called  the  tablet. 
It  is  thus  prepared. 

The  tray  may  be  made  of  tin  or  even  of  paste- 
board or  paper,  and  should  be  about  one  half  an 
inch  deep.  It  may  be  of  any  size,  according  to  the 
work  it  is  to  do.  The  com]3osition  is  made  from 
the  best  gelatine  and  glycerine.  One  ounce  by 
weight  of  gelatine  is  soaked  over  night  in  cold  ^yater, 
and  in  the  morning  the  water  is  poured  off,  leaving 
the  swelled  gelatine.  Six  and  one-half  fluid  ounces 
of  glycerine  are  now  heated  to  about  200  F.  (93  C.) 
on  a water  bath  preferably,  and  the  gelatine  is  added 
thereto.  The  heating  is  continued  for  several  hours. 
This  operates  to  expel  the  water  and  to  give  a clear 
glycerine  solution  of  gelatine. 

The  composition  is  then  poured  into  the  tray. 


122 


nVBBEB  HAND  STAMP  MAKING 


which  must  be  perfectly  level  in  order  to  obtain  a 
a surface  nearly  even  with  the  edge.  It  is  then 
covered  so  as  to  keep  off  the  dust.  The  cover  of 
course  must  not  come  in  contact  with  the  smooth 
surface.  In  six  hours  it  will  be  ready  for  use. 

The  original  copy  that  is  to  be  reproduced  is 
made  upon  ordinary  paper  in  aniline  ink.  One 
formula  for  the  ink  reads  as  follows:  Aniline  violet 
or  blue  (2  R B or  3 B)  1 oz.,  hot  water  7 fluid  oz. ; 
dissolve.  After  cooling  add  alcohol  1 fluid  oz. 
and  glycerine  ^ fluid  oz.,  a few  drops  of  ether  and 
a drop  of  carbolic  acid.  Keep  in  a corked  bottle. 
Other  formulae  are  given  in  chapter  XVII. 

The  writing  is  executed  with  an  ordinary  steel 
pen.  The  lines  should  be  rather  heavy  so  as  to  show 
a greenish  color  by  reflected  light. 

The  surface  of  the  pad  is  slightly  moistened  with 
a wet  sponge  and  is  allowed  to  become  nearly  dry. 
The  paper  is  then  laid  upon  it  and  smoothed  down. 
This  is  best  done  by  placing  a second  sheet  over  it 
and  rubbing  this  with  the  hand.  Xo  air  bubbles 
must  remain  between  the  copy  and  the  tablet,  and 
the  paper  must  not  be  shifted. 

It  is  allowed  to  remain  for  a minute  or  less 
and  is  then  raised  by  one  corner  and  stripped 
from  the  gelatine  surface.  It  will  have  left  the 
reversed  copy  of  its  inscription  perfectly  reproduced 
upon  the  tablet. 

At  once  a piece  of  ordinary  writing  paper  of  the 
desired  size  and  quality  is  laid  upon  the  tablet, 


AND  THE  2IANIPULATI0N  OF  RUBBER.  123 

smoothed  down,  and  stripped  off,  when  it  will  be 
found  to  have  taken  with  it  a complete  copy  of 
the  inscription  or  writing.  This  is  repeated  over 


The  Hektograph. 


and  over  again  with  another  sheet  of  paper,  until 
the  ink  on  the  pad  is  exhausted.  Fifty  or  more 
good  copies  can  be  thus  obtained. 

As  soon  as  the  work  is  completed  the  remains  of 
the  ink  should  be  washerl  off  with  a moist  sponge 


124 


RUBBER  HAND  STAMP  MAKING. 


and  the  tablet^  after  drying  a little,  will  be  ready  for 
a second  operation. 

Some  practice  is  required  to  ascertain  the  proper 
strength  of  the  writing  and  degree  of  wetness  of  the 
surface.  When  the  gelatine  surface  becomes  im- 
paired it  can  be  remelted  in  a water  bath  if  it  is  not 
too  dark  from  absorption  of  ink. 

French  Minister y of  Public  Worh  Formula. — Glue 
100  parts,  glycerine  500  parts,  finally  powdered 
kaolin  or  barium  sulphate  25  parts,  water  375  parts. 
Use  a little  hydrochloric  acid  in  the  water  for 
washing  ofi  the  pad  after  use. 

Hektograph  Sheets. — Four  parts  of  glue  are  soaked 
in  five  parts  of  water  and  three  parts  of  ammonia 
until  soft.  It  is  then  heated  and  there  is  added  to 
it  three  parts  of  sugar  and  eight  parts  of  glycerine. 
The  mixture  is  applied  to  blotting  paper.  This  is 
saturated  with  it,  and  successive  coats  added  until  a 
smooth  surface  is  produced  on  one  side.  This  is 
the  side  for  reproduction.  It  is  used  like  the  regular 
tablet  except  that  it  is  claimed  that  sponging  off 
the  writing  is  not  necessary.  Owing  to  the  capillary 
action  developed  by  the  blotting  paper  it  is  sup- 
posed to  be  self-cleaning  by  standing. 


CHAPTER  XVI. 


CEMENTS. 

Befoke  cementing  vulcanized  rubber  the  surface 
should  be  roughened  or  still  better  it  may  be  seared 
with  a red  hot  iron.  For  bicycle  tyres  this  is  espe- 
cially to  be  recommended. 

Cement  for  Cuts  i7i  Bicycle  Tyres,  Rubber  Belts, 
etc. — Carbon  bisulphide,  5 ounces;  gutta-percha,  5 
ounces;  caoutchouc,  10  ounces;  fish  glue,  2)4 
ounces.  After  it  is  applied  and  has  dried  the 
excess  can  be  removed  with  a wet  knife.  Bad  cuts 
should  first  be  stitched  up. 

Bicycle  Tyre  Cement  to  fasten  Tyres  to  Rims. — 
Equal  parts  of  pitch  and  gutta-percha  are  melted 
together.  Sometimes  two  parts  of  pitch  are  pre- 
scribed. This  cement  has  extended  applica- 
tion. 

Cemeiit  for  Paper  Boats  and  for  Me^iding  Rubber 
Goods. — Fuse  together  equal  parts  of  pitch  and 
gutta-percha,  and  to  this  add  about  2 parts  of  lin- 
seed oil  containing  5 parts  of  litharge.  Continue 
the  heat  until  the  ingredients  are  uniformly  com- 
mingled. Apply  warm. 

Waterproof  Cement. — Shellac,  4 oz;  borax,  1 oz; 


126 


RUBBER  HAND  STAMP  MAKING 


boil  in  a little  water  until  dissolved,  and  concentrate 
by  beat  to  a paste. 

Another. — 10  parts  of  carbon  disulphide  and  one 
part  of  oil  of  turpentine  are  mixed,  and  as  much 
gutta-percha  is  added  as  will  readily  dissolve. 

Cement  for  Mending  Hard  Rubber. — Fuse  together 
equal  parts  of  gutta-percha  and  genuine  asphaltum; 
apply  hot  to  the  joint,  closing  the  latter  immedi- 
ately with  pressure. 

Glue  to  Fasten  Leather,  etc.,  to  Metals. — 1 part 
crushed  nut  galls  digested  6 hours  with  8 parts  dis- 
tilled water  and  strained.  Glue  is  macerated  in  its 
own  weight  of  water  for  24  hours,  and  then  dis- 
solved. The  warm  infusion  of  nutgalls  is  spread 
on  the  leather;  the  glue  solution  upon  the  rough- 
ened surface  of  the  warm  metal;  the  moist  leather 
is  then  pressed  upon  it  and  dried. 

Marine  Glue,  Various  Formulae. — I.  Dissolve  1 
part  of  India  rubber  in  12  parts  of  benzole,  and  to 
the  solution  add  20  parts  of  powdered  shellac,  heat- 
ing the  mixture  cautiously  over  a fire.  There  is 
great  danger  of  confiagration.  Apply  with  a brush. 

II.  Caoutchouc,  1 oz;  genuine  asphaltum,  2 oz; 
benzole  or  naptha,  q.  s.  The  caoutchouc  is  first  dis- 
solved (as  described  in  chapter  XII.),  and  the 
asphaltum  is  gradually  added.  The  solution  should 
have  about  the  consistency  of  molasses. 

Cement  for  Vulcanized  India  Rubber. — Stockholm 
pitch,  3 parts;  American  resin,  3 parts;  un mixed 
india  rubber,  6 parts;  oil  of  turpentine,  12  parts. 


AND  THE  3IANIPULATI0N  OF  RIJBBEE.  127 


Heat  and  mix  very  thoroughly.  More  oil  of  turpen- 
tine may  be  added  as  required. 

Gutta-Percha  Cement  for  Leather. — Soak  gutta- 
percha in  boiling  water.  Soften  in  benzole  after  cut- 
ting up  for  a day.  Heat  on  a water  bath  until  the 
greater  part  of  the  benzole  is  expelled.  When  cool 
it  will  solidify.  Use  by  heating. 

Cement  for  Rubier  Shoes. — 


(1)  Chloroform 280  parts. 

India  rubber  (masticated) 10  “ 

(2)  India  rubber 10  “ 

Kesin 4 “ 

Venice  turpentine 2 ‘‘ 

Oil  of  turpentine 40  “ 


For  first  solution  dissolve  by  mastication.  For 
second^  melt  the  finely  divided  gum  with  the  resin, 
add  the  Venice  turpentine  and  finally  the  oil  of  tur- 
pentine. Use  heat  if  necessary.  Mix  both  solu- 
tions finally.  To  apply,  saturate  a piece  of  linen 
with  the  cement  and  apply  to  the  spot  previously 
coated  with  the  cement.  As  it  dries  apply  a little 
more  as  required.  A finishing  varnish  is  given  in 
the  last  chapter.  Parkes^  cold  curing  process  may 
be  applied  as  described  in  chapter  XI. 

Chattertoyf s Compound  for  uniting  sheets  of 
gutta-percha  in  cable  cores  and  for  general  work 
with  guttarpercha  coated  wires. — Stockholm  tar, 
] part;  resin,  1 part;  gutta-percha,  2 parts. 

Waterproofing  for  Wooden  Battery  Cells. — Resin, 
4 parts;  gutta-percha,  1 part;  boiled  oil,  a little. 


128 


nUBBEB  HAND  STAMP  MAKING. 


Another  Formula. — Barguudy  pitchy  150  parts; 
old  gutta-percha  in  fine  shreds,  25  parts;  ground 
pumice  stone,  75  parts.  Melt  the  gutta-percha  and 
mix  with  the  pumice  stone  and  then  add  the  pitch, 
melting  all  together.  Apply  melted  and  smooth  oft' 
with  a hot  iron. 

Cement  for  Celhiloid. — Shellac,  1 part  is  dissolved 
in  spirits  of  camphor  1 part,  with  3 to  4 parts  strong 
alcohol.  It  is  applied  warm  and  the  parts  united 
must  not  be  disturbed  until  the  cement  is  hard. 


CHAPTER  XVII. 


IX  KS. 

RUBBER  STAMP  IXK. 


Aniline  blue  soluble,  IB 3 parts. 

Distilled  water 10  “ 

Acetic  acid 10 

Alcohol 10 

Glycerine 70 


For  other  colors  the  following  aniline  colors  may 
be  substituted  in  proportions  given: 

Methyl  violet,  3 B (violet) 3 parts. 

Diamond  fuchsin  I,  (red) 2 “ 

Methyl  green  yellowish 4 ** 

Vesuvin,  B (brown) .5  “ 

Xigrosin,  TT  (blue  black) 4 ‘‘ 

For  very  bright  red  3 jiarts  of  Eosin  BBX.  are 
used.  In  this  case  the  acetic  acid  must  be  omitted. 
In  all  cases  the  colors  should  first  he  rubbed  up 
with  the  water  in  a mortar,  and  the  glycerine 
should  be  added  gradually.  These  inks  will  answer 
for  the  hektograph. 

Hektograph  Ink. — Aniline  color,  1 part;  water,  7 
parts;  glycerine,  1 part.  A little  alcohol  may  be 


130 


RUBBER  HAND  STAMP  MAKING 


used  with  advantage  to  dissolve  the  aniline  color. 
It  can  be  expelled  by  heating  if  it  proves  objection- 
able. 

Aniline  Ink  Vehicle. — Prof.  E.  B.  Shuttle  worth, 
of  Toronto,  Out.,  suggests  the  use  of  castor  oil  in 
place  of  vaseline  and  other  vehicles  for  typewriter 
ink.  The  aniline  colors  may  first  be  dissolved  in 
alcohol,  and  the  solution  may  be  added  to  the  oil. 
They  may  also  be  dissolved  directly  in  the  oil  in 
which  most  of  them  are  soluble. 

IndeliUe  Stamjnng  Inks. — I.  Asphaltum,  1 part; 
oil  of  turpentine,  4 parts;  dissolve  and  temper  with 
printers  ink.  The  ink  may  be  omitted,  and  solid 
dry  color  added. 

II.  Sodium  carbonate,  22  parts;  glycerine,  85 
parts;  dissolve  and  rub  up  in  a mortar  with  gum 
arabic,  20  parts.  In  a separate  vessel  dissolve  silver 
nitrate,  II  parts;  in  officinal  aqua  ammonia,  20 
parts.  Mix  the  two  solutions,  and  heat  to  the  boil- 
ing point,  212°  E.  (100°  C.).  After  it  darkens,  add 
Venice  turpentine,  10  parts.  After  applying  to  the 
cloth,  a hot  iron  should  be  applied,  or  it  should  be 
exposed  to  the  sun. 

III.  Dr.  W.  Eeissig^s  formula: 


Boiled  linseed  oil  varnish 16  parts. 

Finest  lamp  black 6 “ 

Ferric  chloride  (sesquichloride  of 

iron) . . 2 to  5 “ 


And  the  manipulation  of  iutbbeb.  131 


Dilute  a little  for  use  with  varnish.  After  this 
ink  has  been  removed,  no  matter  how  completely  it 
can  be  detected  by  dipping  the  paper  into  a solution 
of  ammonium  sulphide. 

IV. 


Aniline  black  in  crystals 1 part. 

Alcohol 80  “ 

Glycerine 80  “ 


Dissolve  in  the  alcohol,  and  add  the  glycerine 
afterwards. 


Shoiv  Card  Ink. — 

Pure  asphaltnni 16  parts. 

Venice  turpentine 18  “ 

Lamp-black 4 “ 

Oil  of  turpentine 64  “ 


Dissolve  the  asphaltum  in  the  turpentine,  and 
thoroughly  mix. 

Stencil  Ink. — Shellac,  2 ounces;  borax,  2 ounces; 
water,  25  ounces.  Dissolve  by  heat  if  necessary, 
first  the  borax  alone,  and  then  adding  the  shellac. 
To  the  clear  solution  add  gum  arabic,  2 ounces. 
Color  with  lamp-black,  with  Venetian  red,  or  with 
ultramarine,  to  suit  the  taste.  Another  formula 
gives  shellac,  4 parts,  borax,  1 part,  and  omits  the 
gum  arabic. 

Copying  Ink  (for  use  without  a press  by  simply 
pressing  and  rubbing  with  the  hand),  by  Prof.  AU- 
field,  F.K.  S. — Use  ink  of  any  kind  of  extra  strength. 


132 


BUBBEH  HAND  STAMP  AIAKINQ 


This  in  many  cases  can  be  made  by  evaporating 
common  ink  down  to  six  tenths  of  its  volume. 
Then  mix  with  it  two  thirds  of  its  volume  of  glycer- 
ine, so  as  to  restore  the  original  volume. 

White  Lilc. — Barium  sulphate^  or  flake  white 
is  mixed  with  gum  arabic  water  of  sufficient  thick- 
ness to  keep  it  suspended,  at  least  while  in  use. 
Starch  or  magnesium  carbonate  or  other  white  pow- 
der may  be  used  instead  of  the  barium  sulphate. 
The  powder  must  be  of  impalpable  flneness. 

White  Ink  on  Blue  Paper. — A solution  of  oxalic 
acid  in  water  is  used  for  this  purpose.  It  may  be 
applied  with  a rubber  stamp  or  with  a common  pen. 
A quill  or  gold  pen  is  the  best  as  a steel  pen  is  soon 
corroded.  The  ink  bleaches  the  paper  wherever  it 
touches  it,  giving  white  lines  on  a blue  ground. 

Gold  Ink. — Gold  leaf  with  honey  is  ground  up  in 
a mortar,  best  an  agate  mortar,  or  on  a painters" 
slab  with  a muller.  It  is  added*  to  water,  and  thor- 
oughly mixed  and  at  once  poured  off  from  the  first 
sediments,  filtered  out,  and  washed.  This  is  done  to 
secure  the  impalpably  finely  ground  gold  only. 
The  resulting  powder  is  mixed  with  a suitable  vehi- 
cle, such  as  white  varnish  or  gum  arabic  water. 

Silver  Ink. — As  above,  using  silver  leaf. 

Zinc  Lalel  Ink. — I.  Verdigris,  1 part;  ammo- 
nium chloride,  1 part;  lamp-black,  ^ part;  water,  10 
parts. 

II.  Platinum  bichloride,  1 part;  gum  arabic,  1 
part;  water,  10  parts. 


AN  I)  THE  MANIPULATION  OF  RUBBEB.  133 


Diamond  Ink  for  Etching  Glass. — This  consists 
essentially  of  liydroflnoric  acid  mixed  with  barium 
sulphate  to  the  consistency  of  cream.  The  barium 
sulphate  is  quite  inoperative  except  as  giving  a body 
to  prevent  the  ink  from  spreading.  It  is  applied 
with  a rubber  stamp  or  pen  and  allowed  to  remain 
for  ten  minutes  or  until  dry.  On  removal  of  the 
white  powder,  the  design  will  be  found  etched  on  the 
glass.  The  following  is  a formula  for  it. 

X Saturate  hydrofluoric  acid  with  ammonia,  add  an 
equal  volume  of  hydrofluoric  acid  and  thicken  with 
barium  sulphate  in  tine  powder. 


CHAPTER  XVIII. 


MISCELLANEOUS. 

To  Soften  and  Restore  India  Rubber  Hose,  etc. — I. 
Dip  ill  petroleum  and  hang  up  for  a couple  of  days. 
Repeat  process  if  necessary. 

II.  The  above  process  is  applicable  to  all  articles, 
but  is  specified  for  hose.  It  is  stated  that  old  rub- 
ber that  has  become  hard  may  be  softened  by  expos- 
ure first  to  vapor  of  carbon  disnljihide,  followed  by 
exposure  to  the  vapor  of  kerosene.  The  latter  vapor  is 
found  to  be  a general  preservative  for  india  rubber. 

III.  Dr.  Pol  recommends  immersion  in  a solution  of 
water  of  ammonia,  1 part,  and  water  2 parts,  from  a 
few  minutes  to  an  hour. 

To  Prevent  Decay  of  Rubber  Tubing. — The  decay 
of  rubber  tubing  has  been  attributed  to  the  forma- 
tion of  sulphuric  acid  from  the  sulphur  mixed 
with  it.  M.  Ballard  has  suggested  washing  with 
water  or  weak  alkaline  solution  five  or  six  times  in 
a year. 

Joints  betiveen  India  Rubber  Tubing  and  Metal. — 
Where  tubing  is  temporarily  slipped  over  metal  gas 
pipes  and  similar  connections,  as  in  the  chemical  lab- 
oratory, it  is  well  to  apply  glycerine  to  the  metal. 


THE  MANIPULATION  OF  RUBBER. 


135 


It  acts  as  a lubricant  in  slipping  the  tubing  on,  and 
assists  in  its  withdrawal. 

Preserving  Vulcanite. — Wash  occasionally  with  a 
solution  of  ammonia  and  rub  with  a rag  slightly 
moistened  with  kerosene  oil. 

Effect  of  Copper  upon  Rubber. — In  a paper  read  be- 
fore the  recent  meeting  of  the  British  Association, 
Sir  William  Thomson  stated  that  metallic  copper, 
when  heated  to  the  temperature  of  boiling  water,  in 
contact  with  the  rubber,  exerted  a destructive  effect 
upon  it.  With  a view  to  finding  whether  this  was 
due  to  the  copper  se,  or  to  its  power  of  conduct- 
ing heat  more  rapidly  to  the  rubber,  he  laid  a sheet 
of  rubber  on  a plate  of  glass,  and  on  it  placed  four 
clean  disks,  one  of  copper,  one  of  platinum,  one  of 
zinc  and  one  of  silver.  After  a few  days  in  an  incu- 
bator at  150°  F.,  the  rubber  under  the  copper  had  be- 
come quite  hard,  that  under  the  platinum  had  be- 
come slightly  affected  and  hardened  at  different 
parts,  while  the  rubber  under  the  silver  and  under 
the  zinc  was  quite  hard  and  elastic.  This  would 
warrant  the  inference  that  the  metallic  copper  had 
exerted  a great  oxidizing  effect  on  the  rubber,  the 
platinum  had  exerted  a slight  effect,  while  the  zinc 
and  silver  respectively  had  no  injurious  influence  on 
it.  The  rubber  thus  hardened  by  the  copper  con- 
tained, strange  enough,  no  appreciable  trace  of  cop- 
per; the  copper,  therefore,  presumably  sets  up  the 
oxidizing  action  in  the  rubber  without  itself  perme- 
ating it. 


186 


miBBm  It  AND  8TAMP  MAKING 


Gas  Tight  Tubings. — Fletcher  has  invented  a gas 
tight  rubber  tubing  in  which  a layer  of  tinfoil  is  in- 
terposed between  two  concentric  rubber  tubes,  all 
vulcanized  together. 

Printing  Colors  upon  India  Rubber. — It  may  some- 
times be  desirable  to  have  a surface  of  vulcanized  In- 
dia rubber  so  prepared  that  it  will  take  colors  such  as 
are  used  for  calico  printing.  This  end  is  simply  at- 
tained by  sprinkling  the  article  with  farina  before 
vulcanizing.  A small  quantity  attaches  itself  and 
forms  an  excellent  base  for  color  printing. 

Gutta-Percha  for  Coating  Glass. — For  focusing 
glass  in  photography  and  for  similar  purposes  where 
ground  glass  or  a translucent  material  is  required, 
a solution  of  gutta-percha  in  chloroform  is  highly 
recommended.  This  is  flowed  over  or  painted  on 
the  glass  and  is  allowed  to  evaporate  afterwards. 

Burned  Rubber. — A very  soft  pure  gum  sold  for 
artists^  use  is  improperly  termed  burned  rubber.  It 
is  used  in  crayon  work  for  removing  and  lightening 
marks  by  dabbing  it  against  the  paper,  cleaning  the 
rubber  from  time  to  time.  It  is  so  soft  that  it  picks 
up  and  removes  crayon  marks  without  the  necessity 
of  friction.  Thus  the  rubbing  out  or  more  properly 
erasing  operation  can  be  localized  and  crayon  tints 
can  be  lightened  in  tone  without  impairment  or 
'‘'smutting.’^  It  is  a very  elegant  accessory  to  the 
artists^  paraphernalia.  To  make  it, pure  virgin  gum, 
preferably  the  best  Para,  is  cut  into  pieces  and  soaked 
for  some  hours  in  benzole.  A long  soaking  is  ad- 


AND  THE  MANIPULATION  OF  RUBBER.  137 

visable.  The  pieces  are  then  removed  from  the  ben- 
zole and  are  ground  in  a mortar  until  perfectly  hom- 
ogeneous. The  mass  is  gathered  up  with  a spatula 
and  is  pressed  into  little  tin  boxes.  If  desired  it 
may  be  dried  upon  a water  bath.  This  is  not  nec- 
essary as,  if  the  box  is  left  open,  it  will  rapidly  season 
itself.  It  should  be  very  soft,  should  tend  to  adhere 
to  the  fingers,  yet  should  leave  them  easily,  and 
should  strip  cleanly  from  the  box.  A very  little 
turpentine  makes  it  more  adhesive.  It  may  even 
be  softened  in  turpentine  alone.  This  gives  a gum 
that  seasons  more  slowly  and  is  in  some  respects  pref- 
erable to  the  benzole  made  preparation.  It  is  sold 
at  a high  price  by  the  dealers,  as  the  demand  for  it  is 
limited. 

Rubher  Sfxmge. — This  is  also  an  artistes  rubber. 
It  is  also  used  for  cleaning  kid  gloves.  It  is  made 
by  incorporating  with  the  masticated  or  washed  and 
sheeted  gum  any  material  or  materials  that  will  give 
off  vapor  in  the  curing  process.  Damp  sawdust  and 
ciTstallized  alum  are  used  as  giving  off  vapor  of 
water  or  steam,  or  ammonium  carbonate  as  giving 
off  vapors  of  ammonia  carbonic  acid  gas  and  steam. 
The  mixed  gum  may  be  cured  in  moulds,  which  it 
will  fill  by  its  expansion. 

Shellac  Varnish  for  India  Rubber. — •This  is  made 
by  soaking  powdered  shellac  in  ten  times  its  weight 
of  strong  aqua  ammonia  (26°  B.).  At  first  no 
change  beyond  a coloring  of  the  solution  is  percep- 
tible. After  many  days  standing  the  bottle,  which 


138 


BUB  BEE  HAND  STAMP  MAKING 


should  have  a glass  stopper^  being  tightly  closed, 
the  shellac  disappears,  having  entered  into  solution. 
It  may  be  a month  before  complete  solution.  This 
forms  an  excellent  varnish  for  India  rubber  shoes 
and  similar  articles.  It  may  be  applied  with  a rag. 
It  is  also  a good  application  for  leather  in  some 
cases  and  doubtless  many  other  uses  could  be 
made  of  it.  It  would  act  well  as  a vehicle  for  a 
dark  pigment  such  as  lamp-black.  It  will  reju- 
venate a pair  of  india  rubbers  very  nicely.  The 
ammonia  exercises  also  a good  influence  on  the  rub- 
ber. It  has  been  recommended  as  a cement  for 
attaching  rubber  to  metal,  but  its  adhesive  powers 
are  not  always  satisfactory. 

Simple  Substitute  for  Sta^nps. — A very  simple 
though  rough  and  imperfect  substitute  may  be 
made  by  gluing  with  common  carpenter^s  glue 
pieces  of  thick  string  upon  a piece  of  wood,  the 
string  being  given  the  form  of  the  desired  letters. 
Care  must  be  taken  to  avoid  saturating  and  stiffen- 
ing the  string  with  the  glue. 

India  Rubber  Substitutes. — One  of  these  under 
the  name  of  vulcanized  oil  is  thus  described  by 
Bolas: 

Vulcanized  oil  is,  perhaps,  of  more  interest,  and 
many  oils,  such  as  linseed  and  others  resembling  it, 
may  be  vulcanized  by  being  heated  for  some  time  to 
150°  Centigrade  with  twelve  to  twenty  per  cent,  of 
sulphur.  The  product  obtained  is  soft,  and  some- 
what resembles  very  bad  india  rubber.  By  increas- 


AXB  THE  UAiVlEULATJO^N^  OE  RUBBER.  139 

ing  the  projjortioii  of  sulphur  very  much  indeed,  say 
to  four  times  the  weight  of  the  oil,  and  vulcanizing 
at  a higher  temperature,  a hard  substance,  resem- 
bling inferior  vulcanite,  is  obtained. 

^^Soft  and  hard  vulcanized  oil  have  been  intro- 
duced into  commerce  at  various  times  and  under 
many  names;  but  these  materials  never  seem  to 
have  made  very  much  headway.'’^ 

Another  method  of  treating  the  oil  consists  in 
mixing  it  with  a solution  of  chloride  of  sulphur  in 
carbon  disulphide  or  in  naptha.  On  standing,  the 
volatile  solvents  escape,  leaving  a thick  mass,  which 
is  the  substitute. 

In  combinations  of  aluminum  with  the  fatty 
acids,  forming  aluminum  soaps,  and  of  these,  alu- 
minum palmitate  especially,  a substitute  for  india 
rubber  has  been  sought  but  without  success. 

Metallized  Caoutchouc. — Un  vulcanized  gum  is- 
mixed  with  powdered  lead,  zinc,  or  antimony.  The 
mixed  india  rubber  is  then  cured  as  in  the  regular 
process. 


EMERY  WHEELS  AiTH  WHETSTONES. 

Bolas  thus  describes  their  manufacture: 

When  ordinary  vulcanized  rubber  is  heated  to 
230°  Centigrade,  (446°  F.)  or  until  it  melts,  a per- 
manently viscous  product  is  obtained,  and  this  sub- 
stance, if  mixed  with  emery  and  sulphur  to  a kind 
of  paste,  forms  a material  out  of  which  the  so-called 
agglomerated  emery  wheels  or  grinders  may  be 


140  KUBBEU  tlANiy  ^TAMP  MAKING 

formed,  the  mixed  materials  being  next  hardened  or 
cured  by  the  application  of  a steam  heat.  Emery 
wheels  and  hones  made  on  this  principle  were  intro- 
duced by  Deplanque  about  twenty-three  years  ago. 

Thirty-five  parts  of  old  vulcanized  caoutchouc 
having  been  placed  in  a kind  of  still,  heat  is  applied 
to  melt  it,  the  operation  being  assisted  by  the  grad- 
ual addition  of  about  ten  parts  of  heavy  coal  oil; 
but  this  latter  is  afterward  distilled  off.  The  soft- 
ened caoutchouc  is  then  incorporated  with  500  parts 
of  emery  of  the  required  degree  of  fineness  and 
nine  parts  of  sulphur.  These  materials  having 
been  thoroughly  mixed,  the  hones  or  wheels  are 
manufactured,  and  afterward  oured  or  baked  at  a 
heat  of  140°  Centigrade,  (284°  F.)  during  a period  of 
about  eight  hours.  Grinding  wheels,  made  in  the 
above  manner,  can  be  worked  at  a speed  of  2,000 
Vevolutions  per  minute,  and  are  extremely  useful 
for  the  working  of  hardened  steel  or  other  obdurate 
materials. 

Etclimg  on  Metals  and  Glass. — India  rubber  stamps 
can  be  used  for  placing  the  ground  upon  knife 
blades  and  similar  articles  which  are  to  be  etched. 
The  parts  untouched  by  the  stamp  are  attacked  by 
the  acid.  In  the  case  of  glass,  diamond  ink  (page 
133)  can  be  put  on  with  a stamp.  The  acids  for 
metal  etching  might  be  thickened  with  barium 
sulphate  also  and  applied  in  the  same  way.  In  these 
cases  the  inscription  of  the  stanip  would  be  etched. 
Where  ground  is  put  on,  whether  on  glass  or 


THE  MAXIPULATIOX  OF  RUBBER.  141 


metal,  the  design  for  the  stamp  will  be  pro- 
tected. 

Etching  Ground  for  Metals. — Equal  parts  of  as- 
phalt, Burgundy  pitch  and  beeswax  melted  together 
and  mixed  thoroughly.  It  may  be  softened  with 
mutton  suet.  Beeswax  may  be  used,  dissolved  in 
ether  or  simply  melted.  Yellow  soap  is  sufficient 
for  ordinary  work. 

Etching  Solutions  for  Biting  in. — For  steel  and 
iron,  a.  sulphate  of  copper  and  common  salt  in  solu- 
tion. h.  sulphate  of  copper,  sulphate  of  alumina, 
and  common  salt,  of  each  two  drachms;  acetic 
acid,  lyi  oz.  c.  sulphuric  acid,  diluted  with  five  vol- 
umes of  water  Avith  a little  sulphate  of  copper. 
For  other  metals,  except  gold  and  platinum,  nitric 
acid  diluted  Avith  five  volumes  of  water. 

Etching  Ground  for  Glass. — Melted  beeswax  is 
generally  recommended.  It  can  be  removed  A\dth 
spirits  of  turpentine  after  as  much  as  possible  has 
been  scraped  off. 

Etching  Glass. — Glass  may  be  conveniently  etched 
by  exposing  it  to  the  vapor  of  hydrofiuoric  acid. 
A shallow  leaden  tray,  as  large  as  the  glass,  is  re- 
quired. A quantity  of  fluorspar  is  placed  in  it  and 
is  moistened  AAuth  concentrated  sulphuric  acid.  The 
glass  is  placed  face  dowuAvard  over  the  tray.  It  is 
supported  over  the  mixture  by  resting  on  the 
edges  of  the  tray  or  b}'  any  simple  method,  and  the 
Avhole  is  covered  Avith  a towel.  In  half  an  hour  or 
more  the  etching  will  be  completed.  The  vapors 


142 


RUBBER  HAND  STAMP  MAKING. 


must  not  be  allowed  to  escape  into  any  room  con- 
taining glass  or  metal  articles  as  they  corrode  every- 
thing. Great  care  should  be  taken  also  not  to  let 
the  mixture  touch  the  hand,  as  painful  ulcers  are 
the  result. 

India  Riohher  Shoe  Blaching. — Kaw  India  rubber 
is  given  as  a constituent  of  several  shoe  blackings. 
Formulae  are  given  as  below  for  paste  and  liquid 
blackings. 

I.  Paste  blacking:  bone-black,  20  parts;  molasses, 
15  parts;  vinegar,  4 parts;  sulphuric  acid,  4 parts; 
caoutchouc  oil  (as  given  below),  3 parts. 

II.  Liquid  blacking:  bone-black,  60  parts;  mo- 
lasses, 45  parts;  gum  arabic  dissolved  in  water,  1 
part;  vinegar,  50  parts;  sulphuric  acid,  24  parts; 
caoutchouc  oil,  9 parts. 

Caoutchouc  oil  is  made  by  dissolving  or  digesting 
virgin  rubber  55  parts  in  linseed  oil  450  parts. 

Waterproof  Composition  for  Boots. — One  ounce  of 
virgin  rubber  cut  into  pieces  is  digested  in  enough 
oil  of  turpentine  to  form  a stiff  paste.  In  applying 
heat  take  great  care  lest  the  contents  of  the  vessel 
become  ignited.  When  homogeneous,  which  con- 
dition may  be  brought  about  by  rubbing  in  a porce- 
lain mortar,  as  described  in  chapter  XII.,  it  is  mixed 
with  5-6  ounces  of  boiled  linseed  oil.  This  gives 
an  ointment  almost  of  the  consistency  of  butter. 


INDEX 


PAGE 

Absorption  of  sulphur  process..  loo 
Absorption  of  water  by  india 

rubber... 31 

Africa,  ways  of  collectings  rub- 
ber sap 15-17 

Analj’sis  of  sap  of  india  rubber 

tree 27 

Apparatus  for  starhp  making.  61-63 
Artists’ burned  rubber 136-137 

Balloons.  . 95 

Bands,  india  rubber  41 

Bicycle  tyre  cement 125 

Blacking,  india  rubber 142 

Borax  and  water  solution  of 

rubber 106-107 

Brazil,  ways  of  collecting  sap.  20-21 

Bromine  as  vulcanizer 100 

Bulbs,  how  made 92-93 

Burned  rubber,  artists’ 136-137 

Calendering 43 

Cane  tips  90 

Caoutchin 30 

Caoutchoucin 30 

Caoutchouc,  (see  India  Rubber.) 

Cements 125-128 

Clamp  for  vulcanizing  press ... . 52 

Cohesion  of  rubber,  its  impor- 
tance to  the  manufacturer..  26-27 
Cold  curing 100-102 


PAGE 

Composition  for  stamps  and  its 


moulding 113-120 

Composition  inking  pad 118-119 

Composition  stamp  handle. . 117-118 

Cord,  rubber  92 

Corks 90-91 

Curing 44 

Curing,  how  to  judge  of  com- 
pletion of 70 

Curing  in  liquid  bath. 97 

Curing  in  sulphur  bath 99 

Curing,  temperature  of  58 

Central  America,  w'ays  of  col- 
lecting rubber 48-19 

Chair  leg  tips 90 

Chalk  plates 83-84 

Chlorine  as  vulcanizer 100 

Chloroform  as  a solvent 105 

Coagulation  of  sap  by  a plant. . . 19 

Coagulation  of  sap  by  alum 22-23 

Coagulation  of  sap  by  fire. . . . 21-22 

Coagulation  of  sap  by  salt 18 

Cohesion  of  pure  rubber 25 


Dating  stamps,  composition.  116-117 
Didot's  polytype  for  matrices..  82-83 
Distillation  products  of  india 


rubber  . 29-30 

Dolls,  how  made . .92-93 

Ebonite 108-111 

Ebonite,  polishing  iio-iii 


144 


INDEX. 


Emery  wheels  and  whetstones 


139-  140 

Emulsion  of  caoutchouc  ic 

Etching 140-142 

Fins,  removal  of — 86 

Flask  for  type  moulding 74 

Flong  matrices 80-82 

Flong  paste 80 

Fluid  for  mixing  with  plaster 
for  matrices 55 

Gas  heated  steam  vulcanizer.. . . 53 

Glue,  marine  126 

Glue  stamps 113-120 

Glycerine  bath  for  curing 97 

Goodyear,  Charles 13-14 

Gutta-percha 111-112 

Gutta-percha,  moulding 111-112 

Gutta-percha,  vulcanizing m 

Hektograph,  composition 


121-122,  124 

Hektograph,  how  made  and 

used 121-124 

Hektograph  ink  (also  see  inks)..  12 1 
Hektograph  sheets 124 

India  Rubber,  absorption  of 

w'ater  by 31 

India  rubber,  African 15-17 

India  rubber,  artists’  burned  136-137 
India  rubber,  availability  for 

small  articles 85 

India  rubber,  cohesion  of  unvul- 
canized  25 

India  rubber,  composition  of 27 

India  rubber,  discovery  of,  etc.  ii-i3 
India  rubber,  effects  of  temper- 
ature on  28-29 

India  rubber,  elasticity  of 

India  rubber  sap,  its  coagula- 
tion   II 


India  rubber  sheet,  how  made..  40 
India  rubbers,  original  way  of 

making 10 

India  rubber  stamp  making  with- 
out apparatus 71 

India  rubber  stamps,  home-made 

mould 48-50 

India  rubber  stamps,  starting 

point 47 

India  rubber,  trees  producing..  9 
India  rubber  tree  sap,  analysis  of  27 

India  rubber  type 73 

India  rubber,  vulcanized,  general 

properties  of 32-33 

India  rubber,  where  collected,  11 
India  rubber,  inelastic,  how 

made 31 

India  rubber,  its  mastication. . 38-40 
India  rubber,  manufacture  of,  35-46 
India  rubber,  necessity  of  dry- 
ing  38 

India  rubber,  points  to  be  fol- 
lowed in  moulding  small  arti- 
cles  85 

India  rubber,  preliminary  opera- 
tions in  manufacturing 35-36 

India  rubber,  preserving,  etc.  134-135 
India  rubber,  properties  of  ... . 28 

India  rubber  sap 9-11 

India  rubber  stamp  vulcanizing  58-60 
Inelastic  state  of  India  rubber..  31 
Inks,  special  for  stamping,etc.  129-133 
Iodine  and  haloid  vulcanizers. . . 100 
Isoprene 30 

Leaves,  skeletonized  as  models.  92 
Liquid  bath  curing 97 

Machine  for  cutting  sheet  and 

threads  40 

Machine  for  making  mixed 
sheet 42-43 


INDEX. 


14o 


Machine  for  masticating 38-40 

Machine  for  washing  and  sheet- 
ing  37 

Mackintosh 13 

Mackintoshes,  how  made 45-46 

Marshmallow  not  for  mixture 

with  plaster 57 

Masticated  rubber,  its  easy  solu- 
tion  103-104 

Masticating  in  mortar  with  ben- 
zole  103-104 

Mastication  of  rubber 38-40 

Materials  mixed  with  india 

rubber 43 

Matrices,  various  kinds  of,  for 

stamps 80-84 

Matrix  for  stamp-making.  ..  54-55 

Matrix  making  by  casting 56-57 

Matrix  press 56 

Matrix,  process  of  making,  for 

stamps 54-55 

Mats 91-92 

Metals,  welding  and  cohesion 

of  25-26 

Miscellaneous  134-142 

Mixed  sheet 42-44 

Mixed  sheet  for  stamps 47-48 

Mould,  home-made  for  stamps.  48-50 
Moulding  and  curing  stamps. . 58-60 
Moulds  for  composition  stamps, 

temperature  of  120 

Moulds,  material  for 86 

Napth.a.  and  volatile  solvents, 

danger  of 107 

Naptha,  solvent 104-105 

Nicaragua,  ways  of  collecting 

sap 19-20 

Nitric  acid  as  vulcanizer 100 

Oil  for  composition  stamp 
moulds  119-120 


Oil  for  mould  face 55 

Oils  fixed  bad  effect  on  solu- 
tions  105 

Oxychloride  of  zinc  cement  for 
matrices 57 

Papier  mache  matrices 80-82 

Paraffin  and  rubber 105-106 

Parkes’  process , 100-102 

Payen’s  solvent 105 

Pencil  tips,  moulds  for 89-90 

Phenyle  sulphide  as  softener  of 

vulcanized  rubber 106 

Plaster  dental  for  matrices 54 


Press  for  moulding  stamps,  etc. 

51-52 

Press,  gas-heated 52-53 

Press,  home-made  49 

Press,  matrix  making 55-56 

Products,  general  division  of..  35-36 

Rods,  stirring  for  laboratory. . . 95 

Rubber,  origin  of  name 12 

Rubber,  .see  India  Rubber 

Salt  bath  for  curing 98 

Sap  of  india  rubber  tree,  analysis 

of 27 

Sheeting  and  washing 37-38 

Sheet  rubber,  how  made 40 

Sheet  rubber,  its  joining 94 

Shellac  for  strengthening  matrix 

Shoes,  blacking  for 142 

Shoes,  india  rubber,  cement  for.  127 

Siphonia,  origin  of  name ii 

Solution,  different  views  of. . . 31-32 

Solution,  difficulties  of 103 

Solvents  for  rubber 104-105 

Spring  chase  for  matrices 56 

Springs  for  stamp  moulds 51 

Springs  on  moulding  press. . . ,.  51 

Sponge  india  rubber 137 

Stamp  making 47 


146 


INDEX. 


Stamps,  rubber,  substitute  for.  138 
Stamps,  see  India  Rubber,  Com- 
position and  general  titles. 
Strauss’  method  of  coagulating 

sap 22-23 

Suction  discs,  regular  mould  for 

88-89 

Suction  discs,  simple  mould  for 

87-88 

Sulphides,  alkaline  as  vulcaniz- 

ers 100 

Sulphur,  absorption  process 100 

Sulphur  bath  for  mixing  and 

curing., 98-100 

Sulphur  chloride  process. . . . 100-102 

Sulphur,  how  mixed  with  gum..  43 
Sulphur,  its  escape  from  vulcan- 
ized rubber .83-34 

Sunlight  excluded  from  washed 

sheet  rubber 38 

Syringes  made  by  Indians ii 

Test  for  curing  with  knife 48 

Thread,  rubber,  cut 41 

Thread,  rubber,  moulded 92 

Tissues,  coated,  how  made 45-46 

Tubes,  connecting  glass 96 

Tube,  seamless 92 

Turpentine,  a solvent  for  vulca- 
nized rubber.  ...  106 

Turpentine  compared  with 

caoutchoucin 30 

Turpentine,  viscid  nature  of 

solution ^ 104-105 

Type,  India  rubber 73 


Type  moulding  flask 74 

Type  and  stamps  from  vulca- 
nized rubber 77 

Type,  cutting  apart  75 

Type,  points  in  moulding 75 

Type,  quads,  and  spaces  for 

stamp  models 71-72 

Type,  steel  moulds  for 76 

United  States  composition 
stamps 113-120 

Varnish  shellac  for  India  rub- 
ber  137-138 

Vulcanite 108-111 

Vulcanization,  its  two  steps 42 

Vulcanization,  steps  in  pro- 
cess  47-48 

Vulcanized  rubber  stamps  and 

type - 77 

Vulcanizer 52-53 

Vulcanizer,  fish  kettle  as  a. ..  69-70 

Vulcanizer,  flower  pot 68-70 

Vulcanizer,  chamber 63 

Vulcanizing  and  moulding 
stamps 58-60 

Washing  and  sheeting 37-38 

Water  absorbed  by  India  rubber.  31 
Waterproof  composition  for 

shoes  142 

Waterproofing  for  battery 
cells 127-128 


Zinc,  chloride 


57 


^lilTUnVIIElTIO 

OIF 


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